NEUROVASCULAR MEDICINE - Pursuing Cellular Longevity for Healthy Aging Part 4 pot

2001.Five years of rhGH replacement therapy in elderly adults with A-OGHD signifi cantly normalized knee fl exor strength 98% to 106% of that predicted and signifi cantly increased, but

forebrains have been characterized (Zhuo, Gebhart

1990a, 1990b, 1991, 1992, 1997; Calejesan, Kim, Zhuo

2000) Biphasic modulation of spinal nociceptive

trans-mission from the RVM, perhaps refl ecting the

differ-ent types of neurons iddiffer-entifi ed in this area, offer fi ne

regulation of spinal sensory thresholds and responses

While descending inhibition is primarily involved in

regulating suprathreshold responses to noxious stimuli,

descending facilitation reduces the neuronal

thresh-old to nociceptive stimulation (Zhuo, Gebhart 1990a,

1990b, 1991, 1992, 1997) Descending facilitation has a

general impact on spinal sensory transmission,

induc-ing sensory inputs from cutaneous and visceral organs

(Zhuo, Sengupta, Gebhart 2002; Zhuo, Gebhart 2002;

Zhuo 2007) (Fig 6.13) Descending facilitation can

be activated under physiological conditions, and one

physiological function of descending facilitation is to

enhance the ability of animals to detect potential

dan-gerous signals in the environment Indeed, neurons

in the RVM not only respond to noxious stimuli, but

also show “learning”-type changes during repetitive

noxious stimuli More importantly, RVM neurons can

undergo plastic changes during and after tissue injury

and infl ammation

ACC-Induced Facilitation

It is well documented that the descending endogenous

analgesia system, including the PAG and RVM, plays

an important role in modulation of nociceptive mission and morphine- and cannabinoid-produced analgesia Neurons in the PAG receive inputs from different nuclei of higher structures, including the cingulated ACC Electrical stimulation of ACC at high intensities (up to 500 µA) of electrical stimulation did not produce any antinociceptive effect Instead,

trans-at most sites within the ACC, electrical stimultrans-ation produced signifi cant facilitation of the TF refl ex (i.e decreases in TF latency) Activation of mGluRs within the ACC also produced facilitatory effects in both anesthetized rats or freely moving mice (Calejesan, Kim, Zhuo 2000; Tang et al 2006) Descending facil-itation from the ACC apparently relays at the RVM (Calejesan, Kim, Zhuo 2000) (see Fig 6.14)

Descending Facilitation Maintains Chronic Pain

Descending facilitation is likely activated after the injury, contributing to secondary hyperalge-sia (Calejesan, Ch’ang, Zhuo 1998; Robinson et al 2002b) Blocking descending facilitation by lesion of the RVM or spinal blockade of serotonin receptors

is antinociceptive (Urban, Gebhart 1999; Porreca, Ossipov, Gebhart 2002; Robinson et al 2004) The descending facilitatory system therefore serves as a

0 1 4 Time (min)

7 10

Figure 6.13 Descending facilitation of spinal visceral pain transmission Example of facilitation of spinal visceral transmission produced by

electrical stimulation and glutamate in the nucleus raphe magnus (NRM) (A) Peristimulus time histograms (1-second binwidth) and responding ocillographic records in the absence (top histograms) and presence (bottom histograms) of electrical stimulation (25 µA) and glutamate (5 nmoles) given in the same site in NRM The intensity and duration of colorectal distension is illustrated below; the period of electrical stimulation (25 seconds) is indicated by the arrows (B) Summary of the data illustrated in (A) and time course of effect of gluta- mate given in NRM The point above c represents the response to 30-mmHg colorectal distension; the point above stimulation represents the response to the same intensity of distension during stimulation in NRM (C) Site of stimulation and injection of glutamate.

C

6 5 4 3

–15

30 20 10

–10 –20

Spinal cord

+: 5-HT

RVM ACC

Figure 6.14 ACC controls RVM-generated descending facilitation (A) A model shows supraspinal control of RVM-generated descending

facilitation of spinal nociception by ACC) neurons (B) An example illustrates that CNQX microinjection into the RVM reversibly blocks facilitation of the TF refl ex produced by electrical stimulation at a site within the ACC; TF response latencies measured without stimula- tion were represented by open squares TF latencies measured with stimulation were represented by fi lled squares; (C) Summary data showing mean facilitation (% of control) before CNQX injection into the RVM (Pre); after (within 10 minutes); and 30 minutes after (30 min post).

double-edged blade in the central nervous system On

one hand, it allows neurons in different parts of the

brain to communicate with each other and enhances

sensitivity to potentially dangerous signals; on the

other hand, prolonged facilitation of spinal

nocicep-tive transmission after injury speeds up central plastic

changes related to chronic pain (Table 6.3)

CONCLUSIONS AND FUTURE

DIRECTIONS

Finally, I would like to review and propose three key

cellular models for future investigations of chronic

pain I would like to emphasize that integrative

experimental approaches are essential for future

studies to avoid the misleading discoveries; work

at different sensory synapses are equally critical

such as spinal cord synapses, cortical synapse, and

brainstem synapses that dictate descending

facilita-tory and inhibifacilita-tory modulations Table 6.4

summa-rizes likely key mechanisms for chronic pain They

of chronic pain Novel mechanisms revealed at ular and cellular levels will signifi cantly affect our future approaches to search and design novel drugs for treating chronic pain in patients

molec-Acknowledgment I thank funding supports from the EJLB-CIHR Michael Smith Chair in Neurosciences

Basbaum AI, Fields HL 1984 Endogenous pain control system: brainstem spinal pathways and endorphin cir-

cuitry Annu Rev Neurosci 7:309–338.

Birbaumer N, Lutzenberger W, Montoya P et al 1997 Effects of regional anesthesia on phantom limb pain are mirrored in changes in cortical reorganization

J Neurosci 17:5503–5508.

Bredt DS, Nicoll RA 2003 AMPA receptor traffi cking at

excitatory synapses Neuron 40:361–379.

Calejesan AA, Ch’ang MH-C, Zhuo M 1998 Spinal tonergic receptors mediate facilitation of a nociecep- tive refl ex by subcutaneous formalin injection into the

sero-hindpaw in rats Brain Res 798:46–54.

and Mental Health in Canada, CIHR operating grants,

Canada Research Chair, and NeuroCanada Brain repair

program.

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Central origin ACC; RVM PAG; RVM

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Stimulation intensity 5–25 µA 50–100 µA

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Michael R Graham, Julien S Baker,

Peter Evans, and Bruce Davies

ABSTRACT

Anabolic–androgenic steroids (AASs) were the fi rst

identifi ed doping agents and can be used to increase

muscle mass and strength in adult males Despite

successful detection and convictions by sporting

antidoping agencies, they are still being used to

increase physical performance and improve

appear-ance Their use does not appear to be diminishing

The adverse side effects and potential dangers of

AAS use have been well documented Recent

epide-miological research has identifi ed that the designer

drugs, growth hormone (GH) and insulin, are also

being used because of the belief that they improve

sporting performance GH and insulin are currently

undetectable by urinalysis The objective of this ter is to summarize the classifi cation of these drugs, their prevalence, and patterns of use The physiology

chap-of GH and its pathophysiology in the disease states

of defi ciency and excess and in catabolic states has been discussed and a distinction made on the differ-ent effects between therapeutic use in replacement and abuse in a sporting context The history, physi-ology, and pathophysiology of insulin in therapeutic replacement and its abuse in a sporting context have also been identifi ed A suggestion has been made on potential mechanisms of the effects of the designer drugs GH and insulin

Keywords: abuse, drugs, GH, insulin, steroids.

WHAT ARE ANABOLIC–ANDROGENIC

STEROIDS?

A nabolic–androgenic steroids (AASs) are a

group of synthetic compounds similar in

chemical structure to the natural anabolic

steroid testosterone (T) (Fig 7.1) (Haupt,

Rovere 1984) T, the predominant circulating

testic-ular androgen, is both an active hormone and a

pro-hormone for the formation of a more active androgen,

the 5α-reduced steroid dihydrotestosterone (DHT)

Physiological studies of steroid hormone

metabo-lism in the postnatal state demonstrated that DHT

is formed in target tissues from circulating T and is

a more potent androgen than T in several bioassay

systems (Wilson, Leihy, Shaw et al 2002)

Genetic evidence indicates that these two

andro-gens work via a common intracellular receptor The

androgen receptor (AR) is an intracellular

ligand-dependent protein that modulates the expression of

genes and mediates biological actions of physiological

androgens (T and 5α-DHT) in a cell-specifi c manner

(Janne, Palvimo, Kallio et al 1993)

During embryonic life, androgens cause the

for-mation of the male urogenital tract and hence are

responsible for development of the tissues that serve as

the major sites of androgen action in postnatal life

It has been generally assumed that androgens

virilize the male fetus by the same mechanisms as in

the adult, namely, by the conversion of circulating T

to DHT in target tissues

A role for steroid 5α-reduction in androgen action

became apparent with the fi ndings in 1968 that DHT,

the 5α-reduced derivative of T, is formed in many

androgen target tissues where it binds to the AR (Bruchovsky, Wilson 1968)

DHT binds to the AR more tightly than T, primarily

as a result of stabilization of the AR complex and at low concentrations is as effective as T is at high concentra-tions in enhancing the transcription of one response element (Deslypere, Young, Wilson et al 1992) This

fi nding clearly indicated that some effects of DHT are the result of amplifi cation of the T signal

Loss of function mutations of the steroid 5

α-reductase 2 gene impairs virilization of the urogenital

sinus and external genitalia in males (Wilson, Griffi n, Russell et al 1993)

In summary, DHT formation both acts as a eral amplifi er of androgen action and conveys specifi c function to the androgen–AR complex The mech-anism by which the specifi c function is mediated is unknown

gen-The enzyme aromatase controls the androgen/estrogen ratio by catalyzing the conversion of T into estradiol (E2) Therefore, the regulation of E2 syn-thesis by aromatase is thought to be critical in sexual development and differentiation (Kroon, Munday, Westcott et al 2005)

Synthetic T was fi rst synthesized from cholesterol

in 1935 (Ruckzika, Wettstein, Kaegi 1935) T is thesized by the interstitial Leydig cells of the testes, which are primarily under the control of the gonado-trophins secreted by the pituitary gland

syn-Approximately 95% of circulating T originates directly from testicular secretion (Ruckzika, Wettstein, Kaegi 1935) Following secretion, T is then trans-ported via the blood to target organs and specifi c receptor sites The bodily functions which are under

Figure 7.1 The structure of testosterone The structural modifi cations to the A- and B-rings of this steroid increase the anabolic activity;

substitution at carbon atom position 17 (C-17) confers oral activity I.M., intramuscular Reproduced with kind permission from Annals of Clinical Biochemistry 2003; 40:321–356.

Attachment of 7α-methyl group

B A

Attachment of 17 α-alkyl group confers oral activity

Esterification confers depot activity for I.M administration

Removal of the angular methyl group

group

In 1993, a report investigating abuse of AASsin

21 gymnasia in England, Scotland, and Wales found that119 (9.1%) of the 1310 male respondents to the questionnaireand 8 (2.3%) of the 349 female respon-dents had taken AASs The youngest abuser was aged

16 The prevalence of abuseof AASs in the gymnasia ranged from 0% (inthree gymnasia) to 46% (28 of 61 respondents) The responserate to the questionnaire was 59% (1677/2834) (Korkia, Stimson 1993)

In 1997, 100 AAS-using athletes were surveyed and high rates of polypharmacy (80%) with a wide array of drug abuse were reported among this sample group (Evans 1997)

Another study in 1996 examined AAS abuse among

176 abusers (171 men and 5 women) and highlighted that 37% of respondents indicated a need for more knowledge of drug effects among drug workers and

a less prejudiced attitude against drug dependency from general practitioners (Pates, Barry 1996)

In 2001, 69% of 107 respondents of hardcore weight lifters were identifi ed as abusing AASs, high-lighting that AAS abuse was certainly not on the decline (Grace, Baker, Davies 2001) Recent surveys conducted by Baker et al (2006)and Parkinson and Evans (2006) have estimated that AASs are being abused by more than 1 million UK citizens and more than 3 million Americans

PREVALENCE AND PATTERNS

OF GROWTH HORMONE AND INSULIN ABUSE

GH appeared in the underground doping literature

in 1981 (Duchaine 1983) Insulin-dependent ics are selling insulin pen-fi lls on the black market to bodybuilders Unused aliquots are being resold, with the added risk of needle sharing and potential HIV and hepatitis C infection

diabet-Extensive literature research identifi es very few cases of rhGH or insulin abuse by athletes The few cases of rhGH abuse that have been published are case histories of individuals who have been arrested

in possession at international tournaments The session of rhGH by the Chinese swimmers bound for the 1998 World Swimming Championships and simi-lar problems at the Tour de France cycling event in

pos-1998 suggested abuse at an elite level (Wallace, Cuneo, Baxter et al 1999) Approximately 1500 vials were stolen from an Australian wholesale chemist 6 months before the Sydney Olympics in 2000 (Sonksen 2001) The few cases of insulin abuse that have been high-lighted are those that have been admitted to hospi-tal following accidental overdose (Konrad, Schupfer, Wietlisbach et al 1998; Evans, Lynch 2003) Dawson (2001) reports that 10% of 450 patients attending his

direct control of T that have relevance to the athlete

can be divided into two broad classifi cations:

Androgenic functions—male hormonal effects

The clinical advantages of a pure anabolic agent

were recognized many years ago and work was

under-taken by a number of drug companies to modify

the T molecule with a view to maximizing the

ana-bolic effect and minimizing the androgenic

activ-ity (Hershberger, Shipley, Meyer 1953) Some of the

structural modifi cations to testosterone to dissociate

the anabolic from the androgenic effects are shown

in Figure 7.1 The extent of the dissociation differs

depending on the modifi cation but there is no AAS

that has an anabolic effect in an athlete without an

androgenic effect (Di Pasquale 1990)

DOPING IN SPORT

AASs were the fi rst identifi ed doping agents to

be banned in sport by the International Olympic

Committee (IOC) Medical Commission in Athens

in 1961 Evidence suggests that they increase muscle

mass and strength and are abused to increase physical

performance and improve appearance (Bhasin et al

1996) The adverse side effects and potential

dan-gers of AAS abuse are well documented (Ferenchick,

Hirokawa, Mammen et al 1995)

The prevalence of AAS use has risen dramatically

over the last two decades and has fi ltered into all aspects

of society Subsequent published work indicated the

concomitant abuse of recombinant human growth

hor-mone (rhGH) and insulin (Grace, Baker, Davies 2001)

Sportspersons are taking rhGH and insulin, separately

or in combination, as doping agents to increase

skele-tal muscle mass and improve performance (Ehrnborg,

Bengtsson, Rosen 2000; Jenkins 2001; Sonksen 2001)

Contemporary research has assessed the effects

of taking supraphysiological levels of rhGH, but has

not assessed the effects of taking rhGH and insulin in

combination in a sporting context Recent research

suggests that rhGH administration in AAS abstinence

may indeed improve sporting performance (Graham,

Davies, Hullin et al 2007b; Graham, Baker, Evans

et al 2008)

THE PREVALENCE OF ANABOLIC–

ANDROGENIC STEROID ABUSE

A questionnaire study conducted by Perry and

Littlepage (1992) found that 39% of 160 respondents

were regular AAS abusers

Cleavage of the GH receptor also yields a lating GH-binding protein (GHBP), which prolongs the half-life and mediates the cellular transport

circu-of GH GH activates the GH receptor, to which the intracellular Janus kinase 2 ( JAK2) tyrosine kinase binds Both the receptor and JAK2 protein are phos-phorylated, and signal transducers and activators of transcription (STAT) proteins bind to this complex STAT proteins are then phosphorylated and trans-located to the nucleus, which initiates transcription

of GH target proteins (Argetsinger, Campbell, Yang

et al 1993)

Intracellular GH signaling is suppressed by several proteins, especially the suppressors of cytokine signal-ing (SOCS) GH induces the synthesis of peripheral insulin-like growth factor 1 (IGF-1) (Le Roith, Scavo, Butler 2001) and both circulating (endocrine) and local (autocrine and paracrine) IGF-1 induce cell proliferation and inhibit apoptosis (O’Reilly, Rojo, She et al 2006)

IGF-binding proteins (IGFBP) and their proteases regulate the access of ligands to the IGF-1 receptor, either enhancing or attenuating the action of IGF-1 Levels of IGF-1 are at the highest during late adoles-cence and decline throughout adulthood; these levels are determined by sex and genetic factors (Milani, Carmichael, Welkowitz et al 2004) The production

of IGF-1 is suppressed in malnourished patients as well as in patients with liver disease, hypothyroidism,

or poorly controlled diabetes IGF-1 levels usually refl ect the secretory activity of GH and IGF-1 is one

of a number of potential markers for identifi cation of rhGH administration in sport (Powrie, Bassett, Rosen

et al 2007)

In conjunction with GH, IGF-1 has varying ential effects on protein, glucose, lipid, and calcium metabolism (Mauras, Attie, Reiter et al 2000), and therefore, on body composition Direct effects result from the interaction of GH with its specifi c receptors

differ-on target cells In the adipocyte, GH stimulates the cell to break down triglyceride (TG) and suppresses its ability to uptake and accumulate circulating lipids Indirect effects are mediated primarily by IGF-1 Many

of the growth-promoting effects of GH are due to the action of IGF-1 on its target cells In most tissues, IGF-1 has local autocrine and paracrine actions, but the liver actively secretes IGF-1 and its binding proteins into the circulation (Mauras, Attie, Reiter et al 2000) Little

is known about the expression of skeletal muscle–

specifi c isoforms of IGF-1 gene in response to exercise

in humans or about the infl uence of age and cal training status Greig et al (2006) reported that a single bout of isometric exercise stimulated the expres-sion of mRNA for the IGF-1 splice variants IGF-1Ea and IGF-1Ec (mechano growth factor [MGF]) within 2.5 hours, which lasts for at least 2 days after exercise

physi-needle-exchange programme self-prescribe insulin

for nontherapeutic purposes The covert nature of its

abuse precludes exact fi gures

A recent questionnaire survey by Baker et al (2006)

has shown an increase in the abuse of insulin from

8% to 14% and an increase in the abuse of growth

hormone (GH) from 6% to 24% in comparison to a

survey conducted by Grace et al (2001)

HISTORY OF GROWTH HORMONE

Physiological Aspects

A cascade of interacting transcription factors and

genetic elements normally determines the ability of

the somatotroph cells in the anterior pituitary to

syn-thesize and secrete the polypeptide human growth

hormone (hGH) The development and proliferation

of somatotrophs are largely determined by a gene

called the Prophet of Pit-1 (PROP1), which controls the

embryonic development of cells of the Pit-1 (POU1F1)

transcription factor lineage Pit-1 binds to the GH

promoter within the cell nucleus, a step that leads to

the development and proliferation of somatotrophs

and GH transcription Once translated, GH is

secre-ted as a 191–amino acid, 4-helix bundle protein (70%

to 80%) and a less abundant 176–amino acid form

(20% to 30%), (Baumann 1991; Wu, Bidlingmaier,

Dall et al 1999) entering the circulation in a pulsatile

manner under dual hypothalamic control through

hypothalamic-releasing and hypothalamic-inhibiting

hormones that traverse the hypophysial portal

sys-tem and act directly on specifi c somatotroph surface

receptors (Melmed 2006)

Growth hormone–releasing hormone (GHRH)

induces the synthesis and secretion of GH, and

soma-tostatin suppresses the secretion of GH GH is also

regulated by ghrelin, a GH secretagogue–receptor

ligand (Kojima, Hosoda, Date et al 1999) that is

syn-thesized mainly in the gastrointestinal tract (GIT)

In healthy persons, the GH level is usually

unde-tectable (<0.2 μg/L) throughout most of the day

There are approximately 10 intermittent pulses of GH

per 24 hours, most often at night, when the level can

be as high as 30 μg/L (Melmed 2006)

Fasting increases the secretion of GH, whereas

aging and obesity are associated with suppressed

secre-tory bursts of the hormone (Iranmanesh, Lizarralde,

Velduis et al 1991)

The action of GH is mediated by a GH receptor,

which is expressed mainly in the liver and in

carti-lage and is composed of preformed dimers that

undergo conformational change when occupied by

a GH ligand, promoting signaling (Brown, Adams,

Pelekanos et al 2005)

GROWTH HORMONE EXCESS

GH excess results in the clinical condition known

as acromegaly This condition is presented as a sequence of a pituitary tumor (Table 7.1) character-ized by a multitude of signs and symptoms (Table 7.2) Pituitary tumors account for approximately 15%

con-of primary intracranial tumors (Melmed 2006) Acromegalics have an increased risk of diabetes mel-litus (DM), hypertension, and premature mortality due to CVD (Bengtsson, Eden, Lonn et al 1993) The nontherapeutic abuse of rhGH by bodybuilders and sportspersons can predispose an individual to the same side effects as are seen in acromegaly, which would appear to be dose dependent Bodybuilders are known

to take supraphysiological doses of as much as 30 IU

of rhGH per day (personal communications), though the average doses abused are much less (Graham, Baker, Evans et al 2007a; Graham, Davies, Hullin et al 2007b; Graham, Davies, Hullin et al 2007c)

The most common side effects following tration arise from sodium and water retention Weight gain, dependent edema, a sensation of tightness in the hands and feet, or carpal tunnel syndrome can frequently occur within days (Hoffman, Crampton, Sernia 1996)

adminis-Arthralgia (joint pain), involving small or large joints can occur, but there is usually no evidence of effusion, infl ammation, or X-ray changes (Salomon, Cuneo, Hesp et al 1989) Muscle pains can also occur

GH administration is documented to result in insulinemia (Hussain, Schmitz, Mengel et al 1993), which may increase the risk of cardiovascular compli-cations GH-induced hypertension (Salomon, Cuneo, Hesp et al 1989) and atrial fi brillation (Bengtsson, Eden, Lonn et al 1993) have both been reported but are rare There have also been reports of cerebral side effects, such as encephalocele (Salomon, Cuneo, Hesp

hyper-et al 1989) and headache with tinnitus (Bengtsson,

GROWTH HORMONE DEFICIENCY

The therapeutic indications for rhGH in the United

Kingdom are controlled by the National Institute

for Clinical Excellence guidelines (May 2002),

which has recommended treatment with rhGH for

child ren with

Growth disturbance in short children born small

•

for gestational age

Proven growth hormone defi ciency (GHD)

function decreased to less than 50%)

NICE (2003) has recommended rhGH in adults

only if the following three criteria are fulfi lled:

Severe GHD established by an appropriate method

hormone defi ciency

Adult-onset growth hormone (A-OGH)–defi cient

individuals are overweight, with reduced lean body

mass (LBM) (Salomon, Cuneo, Hesp et al 1989;

Amato, Carella, Fazio et al 1993; Beshyah, Freemantle,

Shahi et al 1995) and increased fat mass (FM),

espe-cially abdominal adiposity (Salomon, Cuneo, Hesp

et al 1989; Bengtsson, Eden, Lonn et al 1993; Amato,

Carella, Fazio et al 1993; Beshyah, Freemantle, Shahi

et al 1995; Snel, Doerga, Brummer et al 1995) They

have reduced total body water (Black 1972) and

reduced bone mass (Kaufman, Taelman, Vermeuelen

et al 1992; O’Halloran, Tsatsoulis, Whitehouse et al

1993; Holmes, Economou, Whitehouse et al 1994)

There is also reduced strength and exercise capacity

(Cuneo, Salomon, Wiles et al 1990; Cuneo, Salomon,

Wiles et al 1991a; Cuneo, Salomon, Wiles et al

1991b), reduced cardiac performance, and an altered

substrate metabolism (Binnerts, Swart, Wilson et al

1992; Fowelin, Attvall, Lager et al 1993;

Russell-Jones, Weissberger, Bowes et al 1993; O’Neal, Kalfas,

Dunning et al 1994; Hew, Koschmann, Christopher

et al 1996) This leads to an abnormal lipid profi le

(Cuneo, Salomon, Wiles et al 1993; Rosen, Edén S,

Larson et al 1993; De Boer, Blok, Voerman et al 1994;

Attanasio, Lamberts, Matranga et al 1997) that can

predispose to the development of cardiovascular

dis-ease (CVD) A-OGH defi ciency reduces psychological

well-being and QoL (Stabler, Turner, Girdler et al

1992; Rosen, Wiren, Wilhelmsen et al 1994) The

pre-scription of rhGH is currently being used successfully

to treat this defi ciency

Table 7.1 Growth Hormone Excess (Acromegaly)

Primary Growth Hormone Excess

Extra-Pituitary Growth Hormone Excess

Growth Hormone-Releasing Hormone Excess

Pituitary adenoma Pancreatic islet cell

tumor

Central

Hypothalamic tumor Pituitary

carcinoma

Lymphoma Peripheral

Bronchial Pancreatic Lung Adrenal Thyroid Extra-pituitary

tumor

Iatrogenic

Familial syndromes

Effects System System System Systems

Hyper-hydrosis Left ventricular

hypertrophy

Enlarged pituitary

Colon polyps Tongue Reproduction

Thyroid gland Multiple endocrine

neoplasia type 1 Cranial-nerve

palsy

Prognathism/Jaw malocclusion

Skin tags Cardiomyopathy Cranial nerve

palsy

Salivary glands Carbohydratetolerance

Insulin resistance and hyperinsulinemia Diabetes mellitus

Headache Arthralgias and

Spleen Mineral hypercalciuria,

increased levels of 25-hydroxyvitamin D3 and urinary hydroxyproline Hypertrophy of

frontal bones

Kidney Electrolyte

Low renin levels Increased aldosterone levels

Proximal myopathy Prostate Thyroid

Low thyroxine binding– globulin levels Goiter

management of emotional disorder in patients under investigation and treatment in medical and surgical departments (Zigmond, Snaith 1983).

There is a need to assess the contribution of mood disorder, especially anxiety and depression, in order

to understand the experience of suffering in the ting of medical practice Many physicians are aware of this aspect of illness of patients but many feel incom-petent to provide the patient with reliable informa-tion The HADS was designed to provide a simple yet reliable tool for use in medical practice The term

set-“hospital” in its title suggests that it is only valid in such a setting but many studies conducted through-out the world have confi rmed that it is valid when used in community settings and primary care medical practice (Snaith 2003) It should be emphasized that self-assessment scales are only valid for screening pur-poses; defi nitive diagnosis must rest on the process of clinical and psychiatric examination

HADS has also been shown to be a useful instrument for medical patients for screening and examining the disturbed emotion in groups of psy-chosomatic patients (Karakula, Grzywa, Spila et al 1996) Bodybuilders have been described as suffer-ing with an altered perception of body image, leading

to psychiatric morbidity and psychopathology (Pope, Katz 1992; Pope, Phillips, Olivardia 2000)

Bulimia nervosa (characterized by eating binges) and anorexia nervosa (characterized by starvation) have both been linked with bodybuilding, in respect

of the perception of body image Binges are quently followed by self-induced vomiting, laxative and/or diuretic abuse, prolonged fasting, or excessive exercise Some patients with anorexia nervosa also manifest bulimia Unrealistic, overly muscular male body ideals put individuals at risk for negative body images, unhealthy eating and exercise habits, and low self-esteem Some individuals resort to drug taking to counteract their altered body images

fre-Using the Nottingham Health Profi le (NHP) and the Psychological Well-being Schedule (PGWS), McGauley (1989) showed that the QoL improved after

GH administration for 6 months in adults with GHD Decreased psychological well-being has been reported

in hypopituitary patients despite pituitary ment with all hormones but GH (Stabler, Turner, Girdler et al 1992)

replace-There has subsequently been an increasing est in GH-replacement therapy to improve health and QoL of older men with age-related decline in hormone levels A new 21-item age-related hormonal decline (A-RHDQoL) is an individualized question-naire measuring the perceived impact of age-related hormonal decline on the QoL of older men The internal consistency reliability and content validity of the A-RHDQoL are established, but the measure is

inter-Eden, Lonn et al 1993) and benign intracranial

hypertension (Malozowski, Tanner, Wysowski et al

1993) Cessation of GH therapy is associated with

regression of side effects in most cases (Malozowski,

Tanner, Wysowski et al 1993)

THE EFFECTS OF GROWTH HORMONE

ON THE HOSPITAL ANXIETY AND

DEPRESSION SCALE QUESTIONNAIRE

More than 200 published studies worldwide have

reported experiences with the Hospital Anxiety and

Depression Scale (HADS) questionnaire, which was

specifi cally developed by Zigmond and Snaith (1983)

for use with physically ill patients The questionnaire

consists of 14 questions: 7 questions are related to

anxiety and 7 questions are related to depression

Each item is rated from a score of 0 to 3, depending

on the severity of the problem described in each

ques-tion, giving a maximum subscale score of 21 for

anxi-ety and depression, respectively Zigmond and Snaith

(1983) recommended that scores of greater than or

equal to 8 on a subscale should be taken as an

indica-tion of possible psychological morbidity The anxiety

and depression scores are categorized in Table 7.3

The HADS gives clinically meaningful results

as a psychological screening tool, in clinical group

comparisons and in correlational studies with several

aspects of disease and QoL It is sensitive to changes

both during the course of diseases and in response to

psychotherapeutic and psychopharmacological

inter-vention HADS scores predict psychosocial and

pos-sibly physical outcome (Herrmann 1997)

This self-assessment scale was originally developed

and found to be a reliable instrument for detecting

states of depression and anxiety in the setting of a

hospital medical outpatient clinic The anxiety and

depressive subscales are also valid measures of

sever-ity of emotional disorders It was suggested that the

introduction of the scales into general hospital

prac-tice would facilitate the large task of detection and

Table 7.3 Hospital Anxiety and Depression

Scale Questionnaire Scores

Aggregate Score Interpretation

HADS consists of 14 questions: 7 questions are related

to anxiety and 7 questions are related to depression

Each item is rate with a score of 0 to 3, depending on

the severity of the problem described in each question,

giving a maximum subscale score of 21 for anxiety and

depression, respectively.

was no difference between C-OGHD and A-OGHD groups in any variable body composition or isomet-ric or concentric knee extensor strength, knee fl exor strength, left-hand grip strength, or in BMD (Koranyi, Svensson, Götherstrom et al 2001).

Five years of rhGH replacement therapy in elderly adults with A-OGHD signifi cantly normalized knee

fl exor strength (98% to 106% of that predicted) and signifi cantly increased, but did not fully normal-ize, knee extensor strength (90% to 100% of that predicted) and handgrip strength (80% to 87%) (Gotherstrom, Bengtsson, Sunnerhagen et al 2005)

GH-resistant states: When rhGH was given in

con-junction with prednisone, it counteracted the protein catabolic effects of prednisone in eight healthy volun-teers and resulted in increased whole body protein synthesis rates, with no effect on proteolysis (Horber, Haymond 1990) Bowes et al (1997) demonstrated that the clearance of leucine into protein was increased after 2 and 7 days of GH treatment in Cushing’s syn-drome This was consistent with GH stimulating the availability of amino acid transporters However, when large therapeutic doses of rhGH are used in the treatment of cachexia and in HIV wasting syndrome, diabetic symptoms occur relatively more quickly than development of LBM (Schauster, Geletko, Mikolich 2000; Lo, Mulligan, Noor et al 2001)

The infusion of rhGH over 24 hours causes a net glutamine release from skeletal muscle into the cir-culation and increased glutamine synthetase mRNA levels This possibly compensates for reduced glu-tamine precursor availability after trauma in hyper-catabolic trauma patients, which can account for its anticatabolic effects (Biolo, Iscra, Bosutti et al 2000).Hutler et al (2002), demonstrated that GH treat-ment (0.037 to 0.047 mg/kg/day[1 mg = 3 IU])

improved absolute V O2peak during exercise tolerance tests in children with cystic fi brosis (CF), improving exercise tolerance, presumably resulting from the combined effects of GH on the muscular, cardiovas-cular, and pulmonary capacity

RhGH treatment reverses the LBM loss edly responsible for diminished aerobic capacity and symptoms of increased fatigue in patients with HIV-associated wasting It induced LBM gains and improved submaximal measurements but not maxi-mum oxygen uptake in HIV-wasted patients (Esposito, Thomas, Kingdon et al 2005)

alleg-Mechanisms of action: The use of acipimox (an

antilipolytic) with rhGH administration in a 37-hour fasting state eliminated the ability of GH to restrict fasting protein loss, indicating that stimulation of lipolysis by GH is its principle protein-conserving mechanism (Norrelund, Nair, Nielson et al 2003) Muscle protein breakdown increased by 50% (assessed

by labeled phenylalanine) Liu et al (2003) examined

at an early stage of its development and its sensitivity

to change and other psychometric properties needs

to be evaluated in clinical trials of hormone

replace-ment (McMillan, Bradley, Giannoulis et al 2003)

The self-reported HADS questionnaire has been

used extensively to screen psychiatric morbidity

(Janson, Bjornsson, Hetta et al 1994) and has high

validity when it is used as a screening instrument

for this psychiatric condition in outpatients On the

basis of data from a large population, the basic

psy-chometric properties of the HAD scale as a self-rating

instrument should be considered as quite good in

terms of factor structure, intercorrelation,

homoge-neity, and internal consistency (Wilkinson, Barczak

1988; Mykletun, Stordal, Dahl 2001; Martin, Lewin,

Thompson 2003) Current research would suggest

that rhGH may have a benefi cial effect on

psychologi-cal profi le in AAS abuse on withdrawal from AASs

(Graham, Davies, Hullin et al 2007c)

THE EFFECTS OF GROWTH HORMONE

ON ANTHROPOMETRY AND EXERCISE

PERFORMANCE

The administration of rhGH has therapeutic value

as a replacement therapy for GHD adults (Cuneo,

Salomon, Wiles et al 1991a; Cuneo, Salomon, Wiles

et al 1991b; Johannsson, Grimby, Sunnerhagen et al

1997; Carroll, Christ, Bengtsson et al 1998),

increas-ing LBM and reducincreas-ing total and visceral fat, which

may be delayed by up to 12 months V O2peak increased

in A-OGHD after 6 months of replacement therapy

(Cuneo, Salomon, Wiles et al 1990; Cuneo, Salomon,

Wiles et al 1991b; Gullestad, Birkeland, Bjonerheim

et al 1998), 12 months therapy (Borson-Chazot,

Serusclat, Kalfallah et al 1999), and 36 months

ther-apy, which reversed following cessation (Gullestad,

Birkeland, Bjonerheim et al 1998)

The stimulation of erythropoiesis may contribute

as much to the increased exercise performance and

V O2peak (Christ, Cummings, Westwood et al 1997b)

as increased cardiac output (Cuneo, Salomon, Wiles

et al 1991b)

RhGH treatment signifi cantly increased LBM and

bone mineral density (BMD), signifi cantly decreased

total cholesterol (TC) and low-density lipoprotein

cholesterol (LDL-C), and signifi cantly increased

high-density lipoprotein cholesterol (HDL-C),

and results were sustained after 5 and 10 years in

A-OGHD (Gotherstrom, Svensson, Koranyi et al

2001, Gotherstrom, Bengtsson, Bosaeus et al 2007b)

The consequences of GHD differ if the disease is

of childhood onset (C-OGHD) or of adulthood onset

(Koranyi, Svensson, Götherstrom et al 2001) However,

after 5 years of rhGH replacement therapy, there

Measuring the rateof protein synthesis as the rate of incorporation of amino acidslabeled with stable iso-topes into the muscle rather than simplythe changes

in muscle mass between two time points is a more sitive method for determining the response of muscle, but is not freely available (Rennie 2003)

sen-RhGH administration did not enhance the muscle anabolism associated with heavy-resistance exercise

in 16 men aged 21 to 34 years, with a mean weight of 70.6 kg (Yarasheki, Campbell, Smith 1992) The resis-tance training plus rhGH group (0.04 mg/kg/day;

n = 7) did not differ from a resistance training

plus placebo group (n = 9) for 12 weeks (Yarasheki, Campbell, Smith 1992)

The fractional rate of skeletal muscle protein thesis and the whole body rate of protein breakdown did not increase during a constant intravenous infu-sion of [13C]leucine in seven young (mean age: 23 ±

syn-2 years; mean weight: 86.syn-2 kg) healthy experienced male weight lifters before and at the end of 14 days

of subcutaneous rhGH administration, in a dosage of 0.04 mg/kg/day (Yarasheki, Zachwieja, Angelopoulos 1993)

The administration of rhGH in 8 and 10 healthy, nonobese males (mean age: 23.4 ± 0.5 years; mean weight: 122 kg, mean body fat: 10.1%) at a dose of 0.03 mg/kg/day for a period of 6 weeks had no effect on maximal strength during concentric contraction of the biceps and quadriceps muscles (Deyssig, Frisch, Blum et al 1993) In such highly trained power ath-letes with low fat mass there were no effects of rhGH treatment on strength or body composition

RhGH administration at a dose of 0.0125 to 0.024

mg/kg/day (n = 8) versus placebo administration

(n = 15) for 16-weeks did not increase muscle strength over resistance exercise training (75% to 90% maxi-mum strength, 4 days/week) in 23 healthy, sedentary men (mean age: 67 ± 1 years, mean weight: 78.5 kg) with low serum IGF-1 levels (Yarasheki, Zachwieja, Campbell et al 1995)

These results may be consequential to the ferent dosages of rhGH used, because of side effects (0.013 to 0.024 mg/kg/day) The dosages for the fi rst two subjects were equivalent to 1.66 mg/day, but the second two subjects had 1.33 mg/dayand the last four subjects had the equivalent of 1.0 mg/day

dif-RhGH administration (0.03 mg/kg of body weight × 3/week) for 6 months in 52 healthy men (mean age: 75 years, mean weight: 80 kg) with well-preserved functional ability but low baseline IGF-1 levels signifi cantly increased LBM (on average by 4.3%) There were no statistically or clinically sig-nifi cant differences seen between the groups in knee or hand grip strength or in systemic endurance (Papadakis, Grady, Black et al 1996)

Wallace et al (1999) demonstrated that there was

no improvement in morphological or performance

the effects of GH on myostatin (a growth inhibitory

protein) regulation in A-OGHD Skeletal muscle

biopsies from the vastus lateralis were performed at

6-monthly intervals during 18 months of treatment

Myostatin mRNA expression was signifi cantly

inhib-ited to 31% of control by GH The inhibitory effect

of GH on myostatin was sustained after 12 and 18

months of GH treatment These effects were

associ-ated with signifi cantly increased LBM at 6 months,

12 months, and 18 months and translated into signifi

-cantly increased aerobic performance, determined by

V O2peak at 6 months and 12 months

Effects in apparently healthy individuals: GH

secretion and IGF-1 availability diminish with age,

14% per decade (Iranmanesh, Lizarralde, Velduis

et al 1991) The fi rst researchers experimented on

athletes using biosynthetic methionyl hGH

(met-hGH), consisting of 192 amino acids, as opposed to

recombinant (r)hGH (191 amino acids)

The administration of met-hGH (2.67 mg 3 days

per week) for 6 weeks in eight well-trained exercising

adults (22 to 33 years of age) who trained with

progres-sive resistance exercise and maintained a high-protein

diet signifi cantly decreased body fat and signifi cantly

increased fat-free weight (FFW) Five subjects had a

suppressed GH response to stimulation from either

l-dopa or arginine or submaximal exercise (Crist,

Peake, Egan et al 1988)

It was postulated that rhGH administration would

benefi t elderly men, decreasing adiposity and

increas-ing LBM(principally muscle) Rudman et al (1990);

Rudman et al (1991) demonstrated such evidence

Acute administration of rhGH or IGF-1 in

nor-mal healthy humansin the postabsorptive state

sig-nifi cantly increasedforearm net balance of amino

acids (Fryburg, Gelfand, Barrett 1991) The effects

are claimed to occur through the stimulation of

pro-tein synthesis ratherthan through decreased protein

breakdown

However, increased LBM has not been translated

into increased strength or power in healthy

individu-als For example,administration of rhGHappeared to

cause no further increase in muscle mass or strength

than provided by resistance training (RT) in any healthy

young athletes aged 23 ± 2 years (Crist, Peake, Egan

et al 1988; Yarasheki, Campbell, Smith 1992; Yarasheki,

Zachwieja, Angelopoulos 1993; Deyssig, Frisch, Blum

et al 1993) or indeed in healthy elderly men aged

70.2 ± 1.3 or 67 ± 1 years respectively (Taaffe, Pruitt,

Reim et al 1994; Yarasheki, Zachwieja, Campbell et al

1995) There was no substantial evidence that rhGH

could increase strength in healthy men and women

older than 60 years (Zachwieja, Yarasheki 1999)

Muscle protein turnover and increases in muscle

mass can occur over short periods of time (days) and

can be measured indirectly using static techniques such

as hydrostatic weighing or dual X-ray absorptiometry

appearance (Ra) of glycerol at rest and during and after exercise increasedduring treatment with rhGH

as compared with placebo Glucose Raand its rate

of disappearance (Rd) were greater after exerciseduring rhGH treatment as compared with placebo Resting energyexpenditure and fat oxidation were greater under resting conditionsduring rhGH treat-ment compared with placebo

Nine males (mean age: 23.7 ± 1.9 years, mean weight:77.3 kg, mean body fat: 17.7%, mean V O2peak: 37.9 mL/kg/min) completed six,30-minute randomly assigned Monark cycle ergometer exercise trials at

a power output midway between the lactate

thresh-old and V O2peak consumption Subjectsreceived an rhGH infusion (0.01 mg/kg) at 0800 h, followed by

a 30-minute exercisetrial There were no signifi cantcondition effects for total work, caloric expenditure, heartrate response, blood lactate response, or ratings

of perceivedexertion response (RPE) However, acute

GH administration resultedin lower V O2peak without

a drop-off inpower output (Irving, Patrie, Anderson

et al 2004) The reduced V O2peak could not be explained but suggested that GH administration can improve exercise economy This may have been a consequence of production of FFA by GH’s lipolytic effect, providing the substrates for the maintenance

of energy metabolism, despite the lower V O2.There was no increase in strength in 30 physi-cally active and healthy individuals of both genders (15 men and 15 women) of mean age 25.9 years (range 18 to 35) who received rhGH in a dose of 0.033

mg/kg/day (n = 10) and a dose of 0.067 mg/kg/day

(n = 10) versus placebo (n = 10) for 1 month IGF-1

signifi cantly increased by 134% (baseline vs 1 month), body weight signifi cantly increased by 2.7%, fat-free mass signifi cantly increased by 5.3%, total body water (TBW) signifi cantly increased by 6.5%, and extracel-lular water (ECW) signifi cantly increased by 9.6% Body fat signifi cantly decreased signifi cantly by 6.6% (Ehrnborg, Ellegard, Bosaeus et al 2005)

There was no increase in power or oxygen uptake

in 30 physically active and healthy individuals of both genders (15 men and 15 women) of mean age 25.9 years (range 18 to 35) who received rhGH in a dose

of 0.033 mg/kg/day (n = 10) and a dose of 0.067 mg/

kg/day (n = 10) versus placebo (n = 10) for 1 month

(Berggren, Ehrnborg, Rosen et al 2005)

The interaction of GH and 11βhydroxysteroid dehydrogenase (11βHSD1 and 11βHSD2) has been suggested in the pathogenesis of central obesity After

6 weeks of rhGH, the level of 11βHSD1 signifi cantly decreased After 9 months of rhGH, 11βHSD2 level signifi cantly increased Between 6 weeks to 9 months glucose disposal rate increased and visceral fat mass decreased Changes in 11βHSD1 activity correlated with body composition and insulin sensitivity in

30 men (age range: 48 to 66 years) with abdominal

characteristics, assessed by cycle ergometry and

V O2peak assessment, following rhGH administration

(0.05 mg/kg/day; n = 8) versus placebo (n = 8) for

7 days

RhGH administration for 1 month signifi cantly

improved performance in “stair climb time” in 10

healthy older men (Brill, Weltman, Gentili et al 2002)

A single rhGH dose (2.5mg) in seven highly

trainedmen (mean age: 26 ± 1 years; mean weight:

77 kg; mean V O2peak: 65 mL/kg/min) whoperformed

90 minutes of bicycling 4 hours after taking the rhGH

prevented two subjects from completing the exercise

protocol It signifi cantlyincreased plasma levels of

lac-tate and glycerol as well as serum nonesterifi ed fatty

acid (NEFA) levels This may compromise exercise

performance V O2peak remained unaltered by drug

effect until exhaustion (Lange, Larsson, Flyvbjerg

et al 2002b) Plasma glucose was, on average,

signif-icantly higher (9%) duringexercise after GH

admin-istration compared with placebo This would suggest

that any benefi ts of exercise in terms of increased

glu-cose tolerance appeared to be negated by rhGH in the

subjects

RhGH signifi cantly increased the myosin heavy

chain (MHC) 2Xisoforms (Lange, Andersen, Beyer

et al 2002a) Thishas been regarded as a change into a

more youthful MHC composition,possibly induced by

the rejuvenation of systemic IGF-1 levels.RhGH,

how-ever, had no effect on isokinetic quadriceps muscle

strength, power,cross-sectional area (CSA), or fi ber

size RT and placebo caused substantial increases in

the isokineticstrength, power, and CSA of

quadri-ceps; but these RT-induced improvementswere not

further augmented by additional rhGH

administra-tion.In the RT and GH group, there was a signifi cant

decrease in MHC1 and 2X isoforms, whereas MHC

2A increased

RT, therefore,seems to overrule the changes in

MHC composition induced by GH administration

alone

Blackman et al (2002) administered GH at a dose

of 0.03 to 0.02 mg/kg/day and gender-related sex

ste-roids to healthy men and women, aged 65 to 88 for

26 weeks GH with or without sex steroidsin healthy,

aged women and men increased LBM and decreased

fatmass GH with testosterone increased V O2peak in

men, but GH with transdermaloestradiol, 100 µg/day,

plus oral medroxyprogesterone acetate,10 mg/day

did not increase V O2peak in women The effects on

strength and endurance exercise could be attributed

to the effects of testosterone

Healy et al (2003) has shown that rhGH does exert

an anabolic effect both at rest and during exercise in

endurance-trained athletes, measuring whole body

leucine turnover

Healy et al (2003) showed that plasma levels

of glycerol and free fatty acids (FFA) andrate of

could explain why bodybuilders and power lifters self-administer AASs and rhGH together The supra-physiological effect of GH on muscle in patients with acromegaly initiates a GH-resistant state Therefore, true muscle hypertrophy cannot be evaluated since acromegaly is only identifi ed when the pathology becomes fulminant Contemporary evidence would appear to contradict an anabolic effect of rhGH, increasing strength in healthy human muscle in pre-viously non–drug-using subjects The diffi culty lies in targeting an appropriate dose range, given the car-diovascular and metabolic hazards involved.

THE EFFECTS OF GROWTH HORMONE

in healthy controls (Markussis, Beshyah, Fisher et al 1992; Valcavi, Gaddi O, Zini et al 1995) In younger GHD adults, the systolic BP (SBP) has been found to be lower (Thuesen, Jørgensen, Müller et al 1994), but was increased by GH replacement (Theusen, Jørgensen, Müller et al 1994) Short-term, placebo-controlled GH-replacement trials for 4 to 12 months in GHD have demonstrated anabolic effects of GH on cardiac structure (Amato, Carella, Fazio et al 1993; Valcavi, Gaddi O, Zini et al 1995) and benefi cial effects on SBP (Cuneo et al 1991c) There was no change in diastolic

BP (DBP) (Beshyah, Thomas, Kyd et al 1994; Valcavi, Gaddi O, Zini et al 1995) Hoffman et al (1996) have shown a signifi cant increase in body sodium, but not

in plasma volume or BP in GHD adults (n = 7) during

GH replacement at a physiological dosage of 0.013/mg/kg/day and a supraphysiological dosage of 0.027 mg/kg/day for 7 days Other studies have shown no change

in BP between GHD patients and controls before or after replacement therapy (Amato, Carella, Fazio et al 1993; Moller, Fisker, Rosenfalck et al 1999; Pfeifer, Verhovec, Zizek et al 1999) despite the fact that the renin–angiotensin–aldosterone system has been dem-onstrated to be one of the systems responsible for the antinatriuretic effects of GH increasing plasma volume and extracellular fl uid (Moller, Fisker, Rosenfalck et al 1999) A decrease in DBP but not in SBP was demon-strated in female GHD (Bengtsson, Johannsson 1999) Studies have also demonstrated a reduced DBP in men and women as an effect of reduced peripheral vascular resistance (Caidahl, Eden, Bengtsson 1994)

Further studies have found a signifi cant increase

in SBP and DBP after 12 months, but not after 6 months,

obesity However, it was considered that the data could

not support the hypothesis that long-term (9 months)

metabolic effects of GH are mediated through its

action on 11βHSD 1 and 2 (Sigurjonsdottir, Koranyi,

Axelson et al 2006)

Plasma levels of glycerol and FFA increased at rest

and during exercise during rhGH administration at a

dosage of 0.066 mg/kg/day for 4 weeks in 6 trained

male athletes compared to those treated with placebo

This had the effect of signifi cantly increasing resting

energy expenditure and fat oxidation and signifi

-cantly increasing glucose production and uptake after

exercise (Healy, Gibney, Pentecost et al 2006) The

relevance of these effects for athletic performance is

as yet unknown, but one cannot exclude the postulate

that enhancement is possible

The effects of different dosages of rhGH:

Professional bodybuilders and power lifters

admin-ister supraphysiological dosages of the hormone, up

to 0.066 mg/kg/day (Powrie, Bassett, Rosen et al

2007) Despite the knowledge that athletes are

abus-ing these very high dosages, current data has

iden-tifi ed an increase in strength and power (Graham,

Baker, Evans et al 2008) in a cohort of 24 abstinent

AAS-using males taking 0.019 mg/kg/dayrhGH, a

comparatively small supraphysiological dose, versus

24 controls

It is possible that the cohort sizes used by

research-ers have been too low to achieve the results that

are still anecdotally claimed to be as a result of

self- administration However, effects of rhGH have

also been studied at greater than physiological

dos-ages, and although these may well have been below

the dosages abused by bodybuilders, they have still

resulted in serum concentrations of IGF-1 that are at

least twice the normal values (Yarasheki, Zachwieja,

Angelopoulos 1993; Yarasheki, Zachwieja, Campbell

et al 1995) There have been signifi cant

physiologi-cal effects: increased lipolysis, altered carbohydrate

metabolism, activation of the renin–angiotensin

sys-tem, and water retention Mauras et al (2000)

dem-onstrated that when rhGH was given to severely GHD

subjects, both protein synthesis and protein

degra-dation increased with a net anabolic effect Another

explanation for the lack of evidence of increased

strength in apparently healthy individuals is that

rhGH has been reported to have anabolic effects on

bone and collagen metabolism (Bollerslev, Moller,

Thomas et al 1996; Lissett, Shalet 2000) and the

col-lagenous components of skeletal muscle and

connec-tive tissue elements of skin may also show up as new

LBM A small increase in visceral protein and collagen

would equate to an increased positive nitrogen

bal-ance This effect on connective tissue would not

nec-essarily make the muscle generate greater strength or

power, but may enhance resistance to injury or faster

repair, which would be advantageous to athletes This

As observed with other abnormalities associated with GHD, cardiac dysfunction is also susceptible to marked improvement by rhGH (Sacca, Cittadini, Fazio 1994) Attempts have been made by research enthusiasts to extrapolate the anabolic effects of GH in GHD to indi-viduals in a state of senescence (Blackman, Sorkin, Münzer et al 2002) and also to the exercising ath-lete However, few, if any, signifi cant effects have been recorded on BP in athletes, who were either aggressive users of AASs (Karila, Koistinen, Seppala et al 1998)

or previously non–substance users (Healy, Gibney, Russell-Jones et al 2003)

THE EFFECTS OF GROWTH HORMONE

ON HEART RATE

Amato et al (1993) demonstrated no alteration in the heart rate in subjects with GHD, administering 0.01 mg/kg/day, three times per week for 6 months Hoffman et al (1996) and Johannsson et al (1996a) have shown an increase in heart rate at rest in GHD following replacement therapy with rhGH Hoffman

et al (1996) demonstrated that the mean 24-hour heart rate was signifi cantly higher during low-dose (0.013 mg/kg/day) and high-dose (0.027 mg/kg/day) rhGH treatment versus placebo for 7 days (Table 7.4)

Cardiovascular morbidity and mortality are increased in the GH excess condition of acromegaly Both GH and IGF-1 excess induce the hyperkinetic syndrome The resultant concentric biventricular hypertrophy and diastolic dysfunction occurring in such individuals can cause heart failure if untreated (Vitale, Pivonello, Lombardi et al 2004) Recent research has been performed in assessing both the resting and maximal heart rate response to peak exercise in early-onset GH excess following treatment Resting, but not maximal, heart rate was signifi cantly higher pretreatment Following treatment with the

GH antagonist octreotide, a signifi cant reduction in the resting and maximal heart rate was demonstrated, with no amelioration of the elevated peak BP (Colao, Spinelli, Cuocolo et al 2002)

Many researchers have not recorded maximal heart rate differences in healthy athletes who have self- administered rhGH nor demonstrated any adverse effects on the maximal heart rate (Irving, Patrie, Anderson et al 2004) Lange, Lorentsen, Isaksson et al (2001) demonstrated a signifi cant lowering of heart rate after 12 weeks of rhGH administration and exer-cise training in females This contrasted with a signifi -cant increase in heart rate with an acute single dose of

rhGH at 65% V O2peak compared to that with placebo

in males (Lange, Larsson, Flyvbjerg et al 2002b).Research by Ronconi et al (2005) in excess GH dis-ease states has shown an inverse correlation of nitric

of rhGH administration (0.024 mg/kg/day), but only

to the level of the controls Such data would

sug-gest that among other reasons, the BP response has

a dosage-related action over different time intervals

(Johannsson, Bengtsson, Andersson et al 1996a)

An improvement in systolic cardiac function during

exercise has also been demonstrated during rhGH

administration in GHD, suggesting a direct inotropic

and chronotropic action by GH on the heart muscle

(Cittadini, Cuocolo, Merola et al 1994)

GH exerts direct effects on myocardial growth and

function Evidence from laboratory models shows that

GH (or IGF-1) induces mRNA expression for specifi c

contractile proteins and myocyte hypertrophy GH

increases the force of contraction and determines

myosin conversion toward the low adenosine

tripohos-phatase (ATPase) activity V3 isoform This provides

plausible explanations for the cardiac abnormalities

observed in clinical settings of excessive or defective

GH production In acromegaly, the functional

con-sequences of GH excess initially prevail, causing the

hyperkinetic syndrome (high heart rate and increased

systolic output) This is followed by alterations of

car-diac function when myocardial hypertrophy develops

This involves both ventricles and is purposeless because

it occurs without increased wall stress Hypertrophy

also entails proliferation of the myocardial fi brous

tissue that leads to interstitial remodeling (Amato,

Carella, Fazio et al 1993; Sacca, Cittadini, Fazio 1994;

Valcavi, Gaddi O, Zini et al 1995) The functional

con-sequence is an impaired ventricular relaxation that

causes a diastolic dysfunction, followed by impairment

of systolic function In untreated disease, cardiac

per-formance slowly deteriorates and heart failure

even-tually develops Several lines of evidence support the

specifi city of heart disease in acromegaly Particularly

demonstrative are recent studies in which GH

produc-tion was suppressed by octreotide, with a consequent

signifi cant regression of hypertrophy and

improve-ment of cardiac dysfunction (Sacca, Cittadini, Fazio

1994) It is not yet established whether full recovery of

normal cardiac morphology and function is possible

after correction of GH excess GHD leads to a reduced

mass of both ventricles and to impaired cardiac

per-formance with low heart rate (hypokinetic syndrome)

These alterations are particularly evident during

phys-ical exercise and might provide an important

contribu-tion to the reduced exercise capacity of GHD patients,

in addition to the reduced muscle mass and strength

This demonstrates a role of GH in the maintenance

of a normal cardiac structure and performance The

hypokinetic syndrome is well documented in young

patients in whom GHD began very early in their

child-hood (Sacca, Cittadini, Fazio 1994) In contrast, the

data in adult-onset GHD are less consistent This

sug-gests that the consequences of GHD are more relevant

if the disorder starts during early heart development

factor, and some interleukins (ILs) In the poietic process, Epo induces homodimerization of the Epo receptor, which is located on the surface of erythroid progenitor cells Dimerization activates the receptor-associated JAK2 via transphosphorylation Specifi c tyrosines in the intracellular portion of the receptor are phosphorylated and serve as a docking site for intracellular proteins, including one of STAT5 This results in activating various cascades of signal transduction STAT5 enters the nucleus on phosphor-ylation, inducing the transcription of erythroid genes The dephosphorylation of JAK2 and downregulation

erythro-of the Epo receptor are performed by phosphatases Erythropoietin receptor activation seems to exert its effect by inhibiting apoptosis rather than by affect-ing the commitment of erythroid lineage (Mulcahy 2001) Kotzmann et al (1996) demonstrated that patients with GHD do not necessarily have anemia but have hematopoietic precursor cells in the lower nor-mal range RhGH replacement therapy over a period

of 24 months has a marked effect on erythroid and myeloid progenitor precursor cells but negligible effects on peripheral blood cells in GHD

oxide (NO) levels (i.e., a decreased level) with GH and

IGF-1 This suggests that reduced levels of platelet NO

linked to GH excess may contribute to vascular

altera-tions affecting not only heart rate but also endothelial

dysfunction

Current research has shown that

supraphysiologi-cal doses of rhGH administration in apparently healthy

individuals; over a short period of 6 days, there is a

signifi cant elevation of heart rate and corresponding

elevation of rate–pressure product (Graham, Baker,

Evans et al 2007a)

THE EFFECTS OF GROWTH HORMONE

ON HEMOGLOBIN AND PACKED CELL

VOLUME (HEMATOCRIT)

Erythropoietin (Epo) is the primary regulator of

eryth-ropoiesis and promotes the survival, proliferation,

and differentiation of erythroid progenitor cells The

Epo receptor belongs to the same family of receptors

as growth hormone, granulocyte colony-stimulating

factor, granulocyte macrophage colony-stimulating

Table 7.4 Growth Hormone Effects on Blood Pressure and Heart Rate

Effect of GH

Replacement on

Blood Pressure

Effect of GH Replacement on Heart Rate

Effect of GH Replacement on Hemoglobin

Effect of GH Replacement on Glucose

Effect of GH Replacement on Lipid Profi le

et al 1994)

Low Hb present in GHD children (Eugster et al

2002) Increases on replacement (Vihervuori

et al 1996)

Replacement increases liver glycogenolysis (Mauras, Haymond 2005)

to normal in hypotension

in GHD (Theusen et al

1994)

Excess GH in acromegaly results

in hyperkinetic syndrome (increased

HR and increased SBP) (Valcavi et al

1995)

GHD adults have low hematopoietic precursor cells (Kotzmann et al

1996)

GH excess induces β-cell exhaustion and

hemo-despite compensatory hyperinsulinemia In both the basal and insulin-stimulated states (a euglycemic glu-cose clamp) hepatic and peripheral IR is associated with increased lipid oxidation and energy expenditure (Moller, Schmitz, Jørgensen et al 1992) If untreated, this hypermetabolic state will cause pancreatic β-cell exhaustion and DM (Sonksen et al 1967) However, if successfully treated this is reversible (Moller, Schmitz, Jørgensen et al 1992) Only 2 weeks of supraphysi-ological dosages of GH (2.67 mg/day), can induce abnormalities in substrate metabolism and insulin sensiti vity (Moller, Moller, Jørgensen et al 1993).Rizza et al (1982) assessed the mechanisms res ponsible for GH-IR in man He infused GH (2 μgm/kg/h), which increased plasma GH threefold (≈9 ng/mL) within the range observed during sleep and exercise This signifi cantly increased plasma insu-lin concentrations (14 vs 8 μU/mL) without altering plasma glucose concentrations or basal rates of glucose production and utilization Insulin dose–response curves for both signifi cant suppression of glucose pro-duction (half-maximal response at 37 vs 20 μU/mL) and signifi cant stimulation of glucose utilization (half- maximal response at 98 vs 52 μU/mL) were shifted to the right with preservation of normal maximal responses to insulin Monocyte insulin binding was unaffected Thus, except at near maximal insulin receptor occupancy, the action of insulin on glucose production and utilization per number of monocyte insulin receptors occupied was decreased These results indicate that increases in plasma GH within the physiological range can cause

IR in man, which is due to decreases in both hepatic and extrahepatic effects of insulin Assuming that insu-lin binding to monocytes refl ects insulin binding in insulin-sensitive tissues, this decrease in insulin action can be explained on the basis of a post-receptor defect.The GH excess (the acromegalic model) can be used to demonstrate excessive GH states to determine perturbations in metabolism, which may be precipi-tated by rhGH abuse

Johnson and Rennie (1973) demonstrated that exercise in acromegalics caused marked differences in metabolites as compared with controls Concentrations

of glycerol, FFA, and ketone bodies rose rapidly to a maximum during exercise and then decreased dur-ing the period of constant exercise However, it was shown that even in GH excess, insulin retains its effect

on re-esterifi cation of fat in spite of resistance to its effect on carbohydrate metabolism

The known effect of increased serum glucose centrations as a consequence of excess rhGH admin-istration is reversible (Moller, Jørgensen, Møller et al 1995) Its effects on glucose metabolism include sup-pression of glucose oxidation as a consequence of increased lipolysis and ketogenesis resulting in IR in skeletal muscles GH increases the rate of total basal

con-Vihervuori et al (1996) investigated erythropoiesis

in 32 children with short stature and showed that Hb

concentration was positively correlated with relative

body height and with serum IGF-1 and IGFBP-3 levels

but not with the concentrations of Epo Treatment with

rhGH accelerated growth signifi cantly and elevated

Hb, serum IGF-1, and IGFBP-3 signifi cantly When

GHD is associated with multiple pituitary hormone

defi ciencies there are pathological infl uences on

eryth-ropoiesis that are not corrected until rhGH treat ment

is started (Valerio, Di Maio, Salerno et al 1997)

Fetal and early postnatal erythropoiesis are

depen-dent on factors in addition to Epo and the likely

can-didates are GH and IGF-1 (Halvorsen et al 2002)

Hb levels have been shown to be decreased in

chil-dren with GHD compared with age-corrected norms

(Eugster, Fisch, Walvoord et al 2002)

THE EFFECTS OF GROWTH HORMONE

ON GLUCOSE AND LIPID PROFILE

GH stimulates glycogenolysis in the liver in the

main-tenance of a homeostatic level of serum glucose It

decreases glucose uptake by the cell and thereby

decreases glucose use as a substrate for ATP

pro-duction, allowing neurons to continue using

glu-cose for ATP production in gluglu-cose scarcity (Mauras,

Haymond 2005)

Houssay (1936) described the diabetogenic

prop-erties of anterior pituitary hormones initially in classic

animal studies High-dose GH administration reduced

forearm muscle uptake of glucose in normal adults in

the postabsorptive state (Rabinowitz et al 1965) Luft

et al (1968) demonstrated that glycemic control

dete-riorated following a single supraphysiological (10 mg)

dose of GH in hypophysectomized adults with type 1

DM The metabolic effects of a physiological bolus of

rhGH has been studied by Moller et al (1990) in the

postabsorptive state, which demonstrated stimulation

of lipolysis following a lag time of 2 to 3 hours Plasma

glucose demonstrated little fl uctuation, and serum

insulin and C-peptide levels remained stable There

was associated subtle reduction in glucose uptake and

oxidation and substrate competition between glucose

and fatty acids (glucose–fatty acid cycle) However,

high GH levels induced hepatic and peripheral

(mus-cular) resistance to insulin action on glucose

metabo-lism, with associated increase in lipid oxidation

GH-induced insulin resistance (IR) was associated

with diminished glucose-dependent glucose disposal

(Orskov, Schmitz, Jørgensen et al 1989) and reduced

muscle glycogen synthase activity (Bak, Moller,

Schmitz 1991)

Active acromegaly unmasks the diabetogenic effect

of GH In its basal state, plasma glucose is elevated

essential for the energy metabolism of some cells and that conservation of glucose is obligatory for survival

in starvation The overall impact of rhGH treatment

on lipoproteins may have important effects on the cardiovascular mortality in adults with GH defi ciency

A reduction in TC and LDL cholesterol tions reduces the incidence of CVD in both men and women (Levine, Keaney, Vita 1995)

concentra-In contrast to rhGH as a treatment for the somatopause (Savine, Sönksen 2000; Simpson, Savine, Sönksen et al 2002; Lanfranco, Gianotti, Giordano

et al 2003), a recent review (Liu, Bravata, Olkin et al 2007) has highlighted a mean TC decrease by 0.29 mmol/L The clinical signifi cance of these results has been called into question, but a limitation of the study was the mean body mass index (BMI) of 28 kg/m2, which is associated with a blunted response to rhGH (Scacchi, Pincelli, Cavagnini 1999)

THE EFFECTS OF GROWTH HORMONE

ON RESPIRATORY FUNCTION

Physical activity and exercise play a very important part in maintenance of the integrity of the respira-tory system Signifi cantly greater diaphragmatic thickness and maximum inspiratory pressure (MIP) values in resistance trainers compared with non–weight- training adults have been reported (McCool, Conomos, Benditt et al 1997) Insight into the physiology of a forced expiration is an important prerequisite for interpreting spirometry and record-ing a maximum expiratory fl ow-volume curve (Zach 2000)

Pathological disease states—anabolic state; GH excess: It would appear that if acromegaly exceeds

8 years duration, patients develop abnormalities of lung function from the effects of excess GH causing small airways and upper airway narrowing (Harrison, Millhouse, Harrington et al 1978) With current iden-tifi cation and treatment regimes, these progressive conditions are rarely seen today There is an associa-tion between the sleep apnoea syndrome (SAS) and acromegaly, which resolves on treatment of the active condition (Hart, Radow, Blackard et al 1985)

At the opposite end of the scale, increased total lung capacity in acromegaly is reversed after suppres-sion of GH hypersecretion without modifying dif-fusion capacity (Garcia-Rio, Pino, Diez et al 2001) This suggests that lung growth in acromegaly may result from an increase in alveolar size, and not from increased alveolar number or inspiratory muscle strength

A narrow window for GH/IGF-1 levels is required

to maintain optimal respiratory function, as

demon-strated by low V O2peak and ventilation threshold in

glucose turnover whereas oxidative glucose disposal

is signifi cantly decreased (Jorgensen, Pedersen,

Børglum et al 1994)

GH enhances lipolysis in adipose tissue and FFA

use for ATP production GHD patients have been

shown to have elevated concentrations of TC, LDL-C,

and apolipoprotein B (ApoB) HDL-C levels tend to

be low and TG levels high when compared with age-

and sex-matched healthy controls (Rosen, Edén S,

Larson et al 1993) GHD patients appear to have a

lipid profi le associated with premature

atherosclero-sis and CVD

GH replacement results in a signifi cant decrease

in TC (Salomon, Cuneo, Hesp et al 1989; Cuneo,

Salomon, Wiles et al 1993; Attanasio, Lamberts,

Matranga et al 1997) and signifi cant decreases in

LDL-C and ApoB (Russell-Jones, Watts, Weissberger

et al 1994) In addition, there is a signifi cant increase

in HDL-C (Eden, Wiklund, Oscarsson et al 1993;

Attanasio, Lamberts, Matranga et al 1997) The

plasma concentrations of TGs and apolipoprotein

A do not change signifi cantly with replacement

(Salomon, Cuneo, Hesp et al 1989; Weaver, Monson,

Noonan et al 1995; Garry, Collins, Devlin 1996)

Nine months of GH administration in apparently

healthy, abdominally obese men signifi cantly reduced

TC, LDL-C, and apoB levels, but lipoprotein(a) [Lp(a)]

levels signifi cantly increased (Svensson, Bengtsson,

Taskinen 2000) Lucidi et al (2002) demonstrated that

short-term treatment (1 week) with low-dose (0.0025

or 0.0033 mg/kg/day) rhGH stimulates lipolysis in

apparently healthy viscerally obese men, but did not

modify glucose and protein turnover rates

These favorable effects of GH replacement on the

plasma lipid and lipoprotein profi le are sustained for

up to 3 years after commencement (Garry, Collins,

Devlin 1996; Attanasio, Lamberts, Matranga et al

1997)

An exception following GH replacement is the

elevation of Lp(a) concentration There is a strong

relationship between Lp(a) and coronary heart

dis-ease (Angelin, Rudling 1994) GH has elevated Lp(a)

in four out of fi ve studies with no change in one

(Russell-Jones, Watts, Weissberger et al 1994) There

is some evidence that GH replacement upregulates

the hepatic expression of the LDL receptor (Angelin,

Rudling 1994) and may regulate ApoB metabolism

(Christ, Carroll, Russell-Jones et al 1997a)

There is an enhanced fat oxidation rate after

prolonged GH administration (Lange, Lorentsen,

Isaksson et al 2001), supporting the idea that lipid

availability upregulates lipid oxidation, in line with

the Randle Cycle (Randle, Priestman, Mistry et al

1994) This supports the concept that the metabolic

processes in GH administration are akin to those in

fasting or starvation, which stipulates that glucose is

In sport: V

O2peak did not improve during cise in healthy, young males and females with nor-mal GH–IGF-1 axes with low- or high-dose rhGH (Berggren, Ehrnborg, Rosen et al 2005) Current

exer-data has identifi ed an improvement in V O2peak in abstinent AAS abuse (Graham, Davies, Hullin et al 2007b) in a dosage of 0.017 mg/kg/day

High-dose rhGH (0.066 mg/kg/day) has not

dem-onstrated an improvement in V O2peak or athletic performance in endurance-trained athletes (Healey, Gibney, Pentecost et al 2006)

ENDOTHELIAL DYSFUNCTION

IN PATHOLOGICAL GROWTH HORMONE STATES

The potential mechanisms accounting for this mality may result from a direct IGF-1 mediated effect via increased production of NO Qualitative alterations

abnor-in lipoproteabnor-ins have beendescribed in GHD adults (O’Neal, Hew, Sikaris et al 1996), resulting in the generation of anatherogenic lipoprotein phenotype, which would contribute to endothelialdysfunction

GHD: Increased oxidative stress exists in GHD

adults, which may be a factor in atherogenesis, and

is reduced by the effects of GH therapy on tive stress (Evans, Davies, Anderson et al 2000) Endothelial dysfunction exists in GHD adults (Evans, Davies, Goodfellow et al 1999), which is reversible with GH replacement (Pfeifer, Verhovec, Zizek et al 1999) An impaired endothelial-dependent dilatation (EDD) response was documented in GHD adults, which signifi cantly improved after GH treatment.Patients with GHD, with increased risk of vascu-lar disease, have impaired endothelialfunction and increased augmentation index (AIx) compared with controls Replacement of GH resulted in improve-mentof both endothelial function and AIx, without changing BP (Smith, Evans, Wilkinson et al 2002) Administration of rhGH for 3 months corrected endothelial dysfunction in patents with chronic heart failure (Napoli, Guardasole, Matarazzo et al 2002) Lilien et al (2004) showed that endothelial dysfunc-tion in renal failure and GHD is reversed by rhGH therapy Renal failure induces GH resistance at the receptor and post-receptor level, which can be over-come by rhGH therapy

oxida-Growth hormone excess: Acromegaly is

associ-ated with changes in the central arterial pressure waveform, suggesting large artery stiffening This may have important implications for cardiac morphology and performance as well as in increasing the suscepti-bility to atheromatous disease

Smith et al (2003) showed that large artery stiffness

is reduced in “cured” acromegaly (GH <2.5 mU/L)

acromegaly, which improves following treatment with

the GH antagonist, octreotide (Thomas, Woodhouse,

Pagura et al 2002)

Catabolic states; GHD: There is an impairment of

respiratory function in adult patients with C-OGHD,

as a consequence of a reduction of lung volumes and

a decrease of respiratory pressures, probably due

to a reduction of respiratory muscle strength The

impairment in A-OGHD is consequential to a

reduc-tion of respiratory muscle strength Both respond to

replacement therapy with physiological dosages after

12 months (Merola, Longobardi, Sofi a et al 1996)

Respiratory function does not improve in C-OGHD,

with low-dose rhGH (Meineri, Andreani, Sanna et al

1998)

Prader–Willi syndrome (a genetic abnormality of

chromosome 15 with GHD) has demonstrated

sig-nifi cant increases of carbon dioxide (CO2) response,

ventilation, and central inspiratory drive in children

following GH replacement (Lindgren, Hellstrom,

Ritzen et al 1999)

Chronic obstructive pulmonary disease (COPD):

Thirty percent to 60% of patients with COPD are

mal-nourished, which adversely affects ventilatory muscle

function and prognosis for survival

Treatment of malnourished COPD patients with

rhGH has been shown to signifi cantly increase MIP

within 1 week by 27% when provided with controlled

high-protein diets (Pape, Friedman, Underwood

et al 1991) The same effect was not observed after

3 months of high-dose rhGH therapy (Burdet, de

Muralt, Schutz et al 1997) or 6 months of AAS

admin-istration in malnourished COPD patients (Ferreira,

Verreschi, Nery et al 1998)

Cystic Fibrosis: Exercise tolerance has been shown

to improve clinically, but not statistically, on

adminis-tration of biosynthetic rhGH (Huseman, Colombo,

Brooks et al 1996) and also improves signifi cantly in

CF, with rhGH replacement therapy (Hardin, Ellis,

Dyson et al 2001a; Hardin, Ellis, Dyson et al 2001b;

Hutler, Schnabel, Staab et al 2002; Hardin, Ferkol,

Ahn et al 2005) Hutler et al (2002) showed that the

improved effect of rhGH (0.037 to 0.047 mg/kg/day)

on exercise tolerance in children with CF could be

explained by a signifi cant increase in FEV1

Surgical conditions: Respiratory function

improved signifi cantly on rhGH administration in

major surgery, a catabolic condition, and was more

benefi cial when given pre- and postoperatively than

when given postoperatively alone (Barry, Mealy,

O’Neill et al 1999)

Heart failure: Twice daily administration of

Ghrelin (a GH-releasing peptide secretagogue)

impro-ved exercise capacity and left ventricular function in

patients with chronic heart failure (Nagaya, Moriya,

Yasumura et al 2004)

metabolic changes, for example, infl ammatory factors, which develop as a result of long-standing GHD, are of primary importance in the pathogenesis of atheroscle-rosis in patients with GHD Sesmilo et al (2002) dem-onstrated that patients with active acromegaly have signifi cantly lower CRP and signifi cantly higher insulin levels than healthy controls Administration of pegviso-mant signifi cantly increased CRP to normal levels GH secretory status may be an important determinant of serum CRP levels, but the mechanism and signifi cance

of this fi nding is as yet unknown Recent work of others has also demonstrated that infl ammatory markers are predictive of atherosclerosis andcardiovascular events (Ridker, Rifai, Rose et al 2002; Danesh, Wheeler, Hirschfi eld et al 2004; Grace, Davies 2004) Metabolic syndrome (MS) is correlated with elevated CRP and is

a predictor of coronary heart disease and DM (Sattar, Gaw, Scherbakova et al 2003) Leonsson et al (2003) demonstrated that IL-6 concentrations were signifi -cantly increased (208% and 248%) in GHD compared

to BMI-matched and nonobese controls, respectively CRP signifi cantly increased (237%) in patients com-pared to nonobese controls, but not signifi cantly differ-ent compared to BMI-matched controls Age, LDL-C, and IL-6 were positively correlated, and IGF-1 was neg-atively correlated to arterial intima-media thickness (IMT) in the patient group, but only age and IL-6 were independently related to IMT A recent study identi-

fi ed an association between raised HCY levels in term AAS users and sudden death (Graham, Grace, Boobier et al 2006) Both HCY and other risk markers have been shown to decrease in AAS withdrawal and rhGH administration over a 6-day period (Graham, Davies, Hullin et al 2007b)

long-THE EFFECTS OF GROWTH HORMONE

ON BONE MINERAL DENSITY AND BONE METABOLISM

The effects of endocrine dysfunction on BMD are complex and are both disease and site specifi c, hav-ing different effects on the axial and the appendicu-lar skeleton (Seeman et al 1982) Both defi ciency and excess of GH are related to disturbances in calcium metabolism Bone γ-carboxyglutamic acid (Gla) pro-tein (BGP [osteocalcin]) is a specifi c marker of bone turnover identifi ed in peripheral blood

A-OGHD patients have normal initial plasma osteocalcin concentrations Acromegalic patients have signifi cantly increased concentrations of osteocalcin Treatment with rhGH, signifi cantly increases plasma osteocalcin One week after surgery, plasma osteocal-cin concentrations are signifi cantly decreased in acro-megalic patients (Johansen, Pedersen, Jørgensen et al 1990) GHD is associated with reduced bonemass, as

and partially reversed afterpharmacological

treat-ment of active disease

THE EFFECTS OF GROWTH HORMONE

ON INFLAMMATORY MARKERS OF

CARDIOVASCULAR DISEASE

There have been suggestions of an association

between certain infl ammatory markers of CVD and

GHD Human peripheral blood T cells, B cells,

nat-ural killer (NK) cells and monocytes express IGF-1

receptors (Wit, Kooijman, Rijkers et al 1993) Animal

studies suggest a role for GH and IGF-1 in the

modu-lation of both cell-mediated and humoral immunity

Administration of either can reverse the

immunode-fi ciency of Snell dwarf mice (Van Buul-Offers, Ujeda,

Van den Brande 1986) Crist and Kraner (1990)

dem-onstrated that met-hGH induced a signifi cant overall

increase in the percent specifi c lysis of K562 tumor

target cells in healthy adults NK activity was signifi

-cantly increased within the fi rst week and this level

was maintained throughout the remaining period of

administration (6 weeks) In vitro studies using human

lymphocytes indicate that GH is important for the

development of the immune system (Wit, Kooijman,

Rijkers et al 1993) Mealy et al (1998) showed that

preoperative administration of rhGH does not alter

C-reactive protein (CRP, an acute-phase protein,

secreted by hepatocytes in response to invivo infl

am-matory events), serum amyloid A (SAA), or

inter-leukin-6 (IL-6, an infl ammatory cytokine) release

Several studies have established homocysteine (HCY)

concentration as an independent risk factor for

ath-erosclerosis (Eichinger, Stumpfl en, Hirschl et al

1998; Stehouwer, Jacobs 1998) CRP and IL-6 levels

and central fat decreasedsignifi cantly in GH

recipi-ents as compared with placebo recipirecipi-ents in GHD

after 18 months of rhGH However, Lp(a) and glucose

levels signifi cantly increased, without affecting lipid

lev-els (Sesmilo, Biller, Llevadot et al 2000) HCY impairs

vascular endothelial function through signifi cant

reduction of NO production This appears to

potenti-ate oxidative stress and atherogenic development (van

Guldener, Stehouwer 2000) Acute

hyperhomocysteine-mia has been identifi ed in bodybuilders regularly

administering supraphysiological doses of various

AASs (Ebenbinchler, Kaser, Bodner et al 2001) Abdu

et al (2001) demonstrated that HCY levels are not

sig-nifi cantly elevated in GHD adults and are unlikely to

be a major risk factor for vascular disease if there are

no other risk factors present Muller et al (2001)

dem-onstrated that pegvisomant (GH receptor antagonist)

induced no signifi cant acute changes in the major

risk markers for CVD in apparently healthy,

abdomi-nally obese men This suggested that the secondary

shown to increase bone mass in theshort term (3 to 6 months) (Hansen, Brixen, Vahl et al 1996) An openstudy of the effects of 24 months of rhGH replacement

in patients with A-OGHD demonstrated a signifi cant increase in BMD (4% to 10% above baseline) after

2 years of GH treatment,with a sustained signifi cant increase in bone remodeling Serum bone formation (osteocalcin,bone alkaline phophatase, and carboxyl- terminal propeptide of type I procollagen) and urinary resorption markers(deoxypyridinoline, pyri-dinoline, and cross-linked telopeptideof type I colla-gen) all signifi cantly increased (Johannsson, Rosen, Bosaeus et al 1996b) In patients with A-OGHD, bone formation appears to be increased at 6 months,with

no further change throughout treatment (Attanasio, Lamberts, Matranga et al 1997)

In contrast,patients with C-OGHD show a steep increase up to12 months of rhGH therapy, followed by

a sharp decrease to baselinevalue after 18 months of rhGH therapy (Attanasio, Lamberts, Matranga et al 1997) 1,25-Dihydroxyvitamin Dlevel increased in one study after 6 months(Binnerts, Swart, Wilson et al 1992) but was unchanged after 12 monthsin another (Hansen, Brixen, Vahl et al 1996) Hansen reported signifi cant increases in serum phosphate and calciumlevels and signifi cant decreases in Parathormone (PTH) after 6 to 12 months of treatment.PTH did not change after 6 months replacement with rhGH in A-OGHD (Beshyah, Thomas, Kyd et al 1994)

Transiliac bone biopsies of patientswith A-OGHD after 6 to 12 months of rhGH treatmentshowed an increase in cortical thickness, increased bone for-mation,and decreased bone resorption Trabecular bone volume remained unchanged (Bravenboer, Holzmann, de Boer et al 1997)

RhGH treatment in A-OGHD for 10 years induced

a sustained increase in total, lumbar (L2-L4), and femur neck BMD and bone mineral content, as mea-sured by dual energy X-ray absorptiometry (DEXA) Females had an enhanced increase in BMD with estro-gen replacement (Gotherstrom, Bengtsson, Bosaeus

et al 2007a)

GH and IGF-1 excess both stimulate osteoblast proliferation At diagnosis GH excess has usually been present for several years Impaired gonadotrophin secretion with hypogonadism is frequent and may account for decreased BMD Proximal femoral and lumbar spine BMD is normal in most patients with active acromegaly, including those who have hypogo-nadism Successful treatment of acromegaly does not result in major short-term changes in BMD (Ho, Fig, Barkan et al 1992)

Fracture risk was demonstrated to be signifi cantly decreased in patients with acromegaly compared to controls, probably because of the anabolic effect of

GH on bone (Vestergaard, Mosekilde 2004)

assessed by BMD measurements GH acts as an

osteo-anabolic hormone when given toGHD adults The

fi ndings in most of the trials suggestthat GH has a

biphasic effect; after an initial predominanceof bone

resorption, stimulation of bone formation leads to a

net gain in bone mass after 12 to 24 months of

treat-ment.Whether these changes in bone metabolism

will result in less osteopeniaand a reduced fracture

rate in adults with GHD requireslong-term studies

Adults with GHD are at increased risk of

osteopo-roticfractures.Studies have demonstrated reduced

bone mass at different skeletal sites inpatients with

C-OGHD (Kaufman, Taelman, Vermeuelen et al

1992; Hyer, Rodin, Tobias et al 1992; Amato, Carella,

Fazio et al 1993; O’Halloran, Tsatsoulis, Whitehouse

et al 1993), A-OGHD (Bing-You, Denis, Rosen 1993;

Holmes, Economou, Whitehouse et al 1994), and

mixed onset GHD as compared with that inhealthy

control subjects (Thoren, Soop, Degerblad et al 1993;

Beshyah, Freemantle, Shahi et al 1995; Degerblad,

Bengtsson, Bramnert et al 1995).Studies

investigat-ing bone formation (osteocalcin) and resorption

markers(urinary pyridinolines) have yielded

con-fl icting results Osteocalcinlevels have been shown

to be higher (Hyer, Rodin , Tobias et al 1992),

lower (Nielsen, Jørgensen, Brixen et al 1991), or

equal(Johansen, Pedersen, Jørgensen et al 1990) in

patients with A-OGH defi ciency compared with those

in normalcontrols A radiological study of adults

with long-standing GHD demonstratedthat 17% had

reduced vertebral height, consistent with vertebral

fracture, and a further 19% had features of

osteope-nia (Wuster, Slenczka, Ziegler 1991) The fracture

rate in adult patients withGHD, given replacement

therapy other than rhGH, was signifi cantly higher

thanthat in a control population (24.1% vs 8.7%)

(Rosen, Wilhelmsen, Landin-Wilhelmsen et al 1997)

Markers of bone resorption increase in children

with GHD and multiple pituitary defi ciency butnot

in adults with isolated GHD (Schlemmer, Johansen,

Pedersen et al 1991; Sartorio, Conti, Monzani 1993)

It was thought that the presence of other hormones

partially counteracted the negative consequence of

GH–IGF-1 defi ciency However, other studies have

not demonstrated any difference between isolated

GH defi ciency and multiple defi ciency (Holmes,

Economou, Whitehouse et al 1994) Bone histology

of patients with mainly A-OGH defi ciency showed

normal trabecular bone volume, high bone volume

and increased bone erosion, increasedosteoid

thick-ness, and increased mineralization lag time,

indi-catinga delayed bone mineralization (Bravenboer,

Holzmann, de Boer et al 1996)

Signifi cantly reduced BMD has been recorded after

6 or 12 months of rhGH therapy (Holmes, Whitehouse,

Swindell et al 1995) RhGH replacement has not been

decreases serum free T4 and rT3 levels and increases serum T3 levels These changes are independent of TSH and result from increased peripheral conversion

of T4 to T3 A-OGHD does not induce ism but simply reveals previously unrecognized cases whose serum free T4 values fall in the low range during rhGH replacement

hypothyroid-Porretti et al (2002) showed that GHD masks a state of central hypothyroidism in a consistent num-berof adult patients Therefore,during rhGH treat-ment monitoring of thyroid functionis mandatory to start or adjust T4 substitutive therapy.Work by Kalina-Faska et al (2004) did not support the use of thyroid hormone therapy during the fi rst year of rhGH ther-apy in patients who were initially euthyroid

Seminara et al (2005) demonstrated that changes

in thyroid function are present in C-OGHD during long-term rhGH therapy However, these changes probably resulted from the effect of rhGH on the peripheral metabolism of thyroid hormones and appear to be transitory, disappearing during the sec-ond year of rhGH treatment

Alcantara et al (2006) demonstrated untreated GHD due to a homozygous GH-releasing hormone receptor (GHRHR) mutation and that heterozygous carriers of the same mutation have smaller thyroid volume than normal subjects, suggesting that GH has

a permissive role in the growth of the thyroid gland

In addition, GHD subjects have reduced serum total

T3 and increased serum free T4, suggesting a tion in the function of the deiodinase system

reduc-HISTORY OF INSULIN

Sir Edward Schafer, Professor of Physiology in Edinburgh,appears to have been the fi rst to name insulin and describe its actions Hedid so in a book,

The Endocrine Organs, based on a lecture serieshe gave in California in 1913 In his book (Schafer 1916),

he gave the hypothetical substance a name and also described its likely formationfrom activation of an inert precursor “pro-insuline.” Insulin was subse-quently discovered by Banting and Best in 1921.The

fi rst patient was treated a year later in 1922 and insulin was discovered (and renamed) more than

pro-50 years later by GeorgeSteiner of the University of Chicago in 1967 Schafer deliberately avoided using the word “hormone”and used his preferred terms

“autacoid” (excitatory) and “chalonic” (inhibitory).This was as a result of long-standing academic rivalry withhis contemporaries Professors Baylis and Starling

at UniversityCollege, London They had previously described “secretin” as thefi rst hormone to be isolated and characterized They had coinedthe term “hor-mones” to describe the class of substanceproduced in

A disadvantageous effect of acromegaly is

decreased BMD This is thought to be due to

associ-ated hypogonadism It has been shown to occur in

the distal radius (in women), the proximal femur (in

men), and the total body, in both sexes (Bolanowski,

Daroszewski, Medras et al 2006) An anabolic effect of

GH during active acromegaly has also been shown in

the proximal femur in eugonadal men (Bolanowski,

Daroszewski, Medras et al 2006)

THE EFFECTS OF GROWTH HORMONE

ON THYROID FUNCTION

GH infl uences thyroid function and anatomy Goiter is

frequent in acromegalic patients The effects of GHD

are diffi cult to assess because hypopituitary subjects

who lack GH often also have a partial or complete

def-icit of thyroid-stimulating hormone (TSH)

The occurrence of central hypothyroidism in

previ-ously euthyroid childrenduring GH therapy has been

reported with widely varying incidence The actual

incidence is controversial, however,with some studies

showing a high occurrence (Goodman, Grumbach,

Kaplan 1968; Lippe, Van Herle, LaFranchi et al 1975;

Stahnke, Koehn 1990) and others little (Cacciari,

Cicognani, Pirazzoli et al 1979)

RhGH is known to increase the metabolism of

thyroxin (tetra-iodothyronine [T4]), enhancing

the conversion of T4 to triiodothyronine (T3) (Sato,

Suzukui, Taketani et al 1977) The lowering of

serum free T4 supported the work of Grunfeld et al

(1988) where T4 was signifi cantly lowered by 8%, T3

was signifi cantly increased by 21%, and TSH was

sig-nifi cantly decreased by 54% after 4 days of low-dose

rhGH administration (0.125 mg/day) The work of

Moller et al (1992), Jorgensen et al (1994), and Wyatt

et al (1998) demonstrated that T4 was unaltered after

12 months of rhGH replacement therapy

Wyatt et al (1998) showed that shifts in thyroid

hormone levels are very commonduring the fi rst year

of GH therapy in children who are initiallyeuthyroid

Baseline TSH, T4, free T4, reverse (r)T3,and T3 levels

werenormal with negative antithyroid antibodies By

1 month, there were signifi cant decreasesin T4, free T4

index, and rT3, and signifi cant increases inT3 and the

T3/T4 ratio The changes from baseline values were

greatest at 1 month, butshowed a gradual return to

baseline from 3 to 12 months.There were no clinical

signs of hypothyroidism T4 supplementationis seldom

needed in such patients

Ito et al (1998) demonstrated a signifi cant increase

in serum thyroid hormone during and after a 5-day

administration of human GH in healthy male adults

Portes et al (2000) demonstrated that long-term

rhGH replacement therapy in A-OGHD signifi cantly

Much of the “free” intracellular glucose transported into the cell is transported back out of the cell into the extracellular fl uid Under conditions of ketoaci-dosis, glucose metabolism (but not glucose uptake) is impaired as a direct consequence of the metabolism of fat, the “glucose–fatty acid” or Randle cycle (Randle, Priestman, Mistry et al 1994).

In Figure 7.2 it can be seen that simultaneously with the excitatory effect in stimulating lipogenesis insulin also exhibits an inhibitory effect in preventing glycerol release It is this inhibitory effect on lipolysis (and also glycolysis, gluconeogenesis, ketogenesis and proteolysis) that accounts for most of insulin’s physi-ological effects in vivo in man The inhibitory effects are also responsible for insulin’s net anabolic actions.The introduction of dynamic tracer studies enabled the identifi cation of insulin’s action in vivo in man (Sonksen, Sonksen 2000) Glucose infusion labeled with either radioactive or stable isotopes allowed the accurate measure of the rates of glucose production (rate of appearance, Ra) and rates of glucose utiliza-tion (rate of disappearance, Rd) in the circulating blood Uncontrolled diabetics demonstrated that fast-ing hyperglycemia was associated with rates of glucose appearance that were increased several fold above normal (Sonksen, Sonksen 2000) Fasting glucose uptake was also increased Since the fasting hypergly-cemia in diabetes is sustained and there is a “dynamic steady state” where Ra = Rd; thus, both Ra and Rd are elevated

In diabetes fasting blood glucose is an accurate measure of the severity of insulin defi ciency There

is a linear correlation between the fasting blood cose and the rate of hepatic glucose production (Ra)

glu-one part of the body and acting elsewhere Schafer

preferred his own terms, which were based on terms

used at thetime to describe actions of drugs, autacoid

beinga substance with excitatory action and chalone

being one with inhibitory action.Schafer went on to

describe how insuline had bothexcitatory and

inhib-itory actions His description of how hethought the

hypothetical substance insuline actedin the body is

remarkable because the passage of time has shown

him to be correct almost word for word

PHYSIOLOGY OF INSULIN

Insulin is a two-chain (30 and 21 amino acids)

poly-peptide hormone (51 amino acids; molecular weight,

5808) synthesized and secreted by the β-cells of the

islets of Langerhans in the pancreas gland Insulin

acts in a stimulatory and an inhibitory manner

(Schafer 1916) It stimulates the translocation of “Glut

4” glucose transporters from the cytoplasm of muscle

and adipose tissue to the cell membrane This

stimu-lation increases the rate of glucose uptake to values

greater than those in the basal state without insulin

shown in isolated adipocytes from rats, as illustrated

in Figure 7.2

Insulin exhibits both inhibitory (chalonic) and

excitatory (autacoid) actions via the same receptor

In these experiments carried out on rat adipose

tis-sue, in vitro insulin simultaneously inhibits lipolysis

(the release of glycerol from stored TG) and

stimu-lates lipogenesis (formation of stored TG from

glu-cose) (Table 7.5) Thus its anabolic action is due to

two mechanisms working synergistically (Thomas,

Wisher, Brandenburg et al 1979)

There are suffi cient numbers of glucose

transport-ers in all cell membranes at all times to ensure enough

glucose uptake to satisfy the cell’s respiration, even in

the absence of insulin Insulin increases the number of

these transporters in some cells but glucose uptake is

never truly insulin dependent (Sonksen 2001) Even in

uncontrolled diabetic hyperglycemia, whole body

glu-cose uptake is increased (unless there is severe

keto-sis) Even under conditions of severe ketoacidosis there

is no membrane barrier to glucose uptake The block

occurs where the excess ketone concentration

compet-itively blocks the metabolites of glucose entering the

Krebs cycle (Sonksen 2001) Glucose is therefore freely

transported into the cell, but the pathway of

metab-olism is blocked at the entry point to the Krebs cycle

by the excess of metabolites arising from fat and

pro-tein breakdown As a result of this competitive block

at the entry point to the Krebs cycle, intracellular

glucose metabolites increase throughout the glycolytic

pathway, leading to accumulation of free intracellular

glucose and inhibiting initial glucose phosphorylation

Figure 7.2 The anabolic actions of insulin Insulin increases the

rate of glucose uptake to values greater than that in the basal state without insulin; shown in isolated adipocytes from rats and

is illustrated in Figure 7.2 Key: ○ = Glucose converted into Lipid;

● = Glycerol released (Thomas, Wisher, Brandenburg et al 1979; Sonksen 2001).

and fat soluble and distribute within body water and body fat Both ketones and FFA compete with glucose

as energy substrate at the point of entry into the Krebs cycle Glucose metabolism increases inevitably as FFA and ketone levels fall (despite the concomitant fall in plasma glucose concentration) (Sonksen 2001)

As a consequence, insulin increases glucose metabolism more through reducing FFA and ketone levels than it does through recruiting more glucose transporters into the muscle cell membrane Insulin does have a direct action recruiting more glucose transporters into muscle cell membranes This facili-tates glucose uptake, which is refl ected as an increase

in the metabolic clearance rate (MCR) of glucose The MCR measured with tracer technology is a very important physiological measurement It is defi ned as

“the amount of blood irreversibly cleared of glucose

in unit time.” It is expressed normally in mL/kg/min and is a nonlinear function of blood glucose concen-tration (increasing as glucose concentration falls) and is highly sensitive to insulin (increasing with increasing insulin levels) (Sonksen, Sonksen 2000)

It is measured relatively noninvasively in vivo using nonradioactive tracers or stable isotopes All polar (water-soluble) substrates, as “transporters” are the mechanism by which they are transported across the highly nonpolar (lipid) cell membranes The entry

of a water-soluble substrate such as glucose across an impermeable lipid bilayer into a cell requires a spe-cifi c transport mechanism These protein carriers are the glucose “transporters” (GLUTs) In the case

of glucose, there are at least six types and they tend

to be tissue specifi c In the case of muscle, the

trans-porter is called Glut 4 It is normally present in excess

in the cell membrane even in the absence of lin and is not rate limiting for glucose entry into the cell (Sonksen 2001) Glucose transport into the cell

insu-is mainly determined by the concentration gradient between the extracellular fl uid and the intracellular

and the rate of glucose disappearance (Rd) (Sonksen,

Sonksen 2000) The fasting blood glucose exceeds the

renal threshold; not all glucose leaving the circulation

is actually being metabolized By collecting the urine

and quantifying the urinary glucose losses it is easy to

measure the true rate of glucose utilization and the

rate of urinary glucose loss Glycosuria can account for

as much as 30% of glucose turnover After correcting

whole body glucose turnover for urinary glucose losses,

tissue glucose utilization is increased in diabetes

com-pared with normal (Sonksen, Sonksen 2000) Insulin is

not needed for glucose uptake and utilization in man,

that is, glucose uptake is not totally insulin dependent

When insulin is administered to people with

diabe-tes who are fasting, blood glucose concentration falls

Insulin, at concentrations that are within the normal

physiological range, lowers blood glucose by inhibiting

hepatic glucose production (Ra) without stimulating

peripheral glucose uptake (Brown, Tomkins, Juul et al

1978) As hepatic glucose output is “switched off” by the

inhibitory action of insulin, glucose concentration falls

and glucose uptake actually decreases Glucose uptake

is actually increased in uncontrolled diabetes and

decreased by insulin administration (Sonksen 2001)

Even in insulin defi ciency, there are suffi cient glucose

transporters in the cell membranes The factor

deter-mining glucose uptake under these conditions is the

concentration gradient across the cell membrane; this

is highest in uncontrolled diabetes and falls as insulin

lowers blood glucose concentration primarily (at

phys-iological insulin concentrations) by reducing hepatic

glucose production When insulin is given to patients

with uncontrolled diabetes, it switches off a number of

metabolic processes (lipolysis, proteolysis, ketogenesis,

and gluconeogenesis) by a similar inhibitory action

The result is that FFA concentrations fall effectively to

zero within minutes and ketogenesis inevitably stops

through lack of substrate It takes some time for the

ketones to clear from the circulation, as they are water

Table 7.5 Physiological and Pathological Effects of Insulin

Physiological Effects of Insulin

Insulin inhibits lipolysis & stimulates lipogenesis (Thomas et al 1979)

Pathological Effects of Insulin Insulin Resistance Hyperinsulinemia

Increases visceral

obesity

(Nyholm et al 2004)

Increases athero sclerosis (Meissner, Legg 1973)

Increases heart rate

(O’ Hare et al

1989)

Increases blood pressure (Scott et al 1988)

Increases Hb and PCV (Facchini et al

1998)

Decreases respiratory function

(Lazarus et al 1998a)

Increases sympathetic nervous system activity (Landsberg 1986)

Increases renal sodium reabsorption (DeFronzo 1981)

Hb, hemoglobin; PCV, packed cell volume.

studied at the same insulin concentrations, but with plasma glucose increased and maintained at a steady level by an exogenous glucose infusion Four glucose concentrations ranging from 5 to 10 mmol/Lwere studied with insulin levels maintained at normal fast-ing values During the insulin infusions, subjects were studied at three glucose concentrations spanning the same range Using tracer methodology, the authors were able to calculate Ra, Rd, and MCR at each glu-cose and insulin concentration (Fig 7.3) (Gottesman, Mandarino, Verdonk et al 1982; Sonksen 2001) The important points of note are as follows:

Total glucose uptake (Rd) is a nonlinear function

1

of blood glucose concentration Initially, uptake increases as blood glucose concentration rises but plateaus at higher glucose concentration Although detectable within the range of glucose concentra-tions studied, it is made more obvious through extrapolation to higher glucose concentrations by use of the model These high glucose values are unobtainable in normal subjects with existing

“free” glucose Free glucose is very low inside the cell

as it is immediately phosphorylated In uncontrolled

diabetes, particularly where there is a high

concentra-tion of FFA and ketones, glycolysis is inhibited,

phos-phorylation of free glucose stops, and intracellular

free glucose rises Insulin recruits more transporters

into the cell membrane from an intracellular pool

This increases the rate of glucose entry for a given

glu-cose concentration and this is refl ected in vivo by an

increase in the MCR of glucose Thus MCR is an in vivo

measure of substrate transporter activity (Boroujerdi,

Umpleby, Jones et al 1995) Experiments in normal

subjects using hyperglycemic and hyperinsulinemic

“clamps” have shown the importance of both glucose

and insulin concentrations in determining glucose

uptake Studies illustrating these points are shown

in Figure 7.3 (Gottesman, Mandarino, Verdonk et al

1982) Subjects were studied in the overnight-fasted

state with fasting insulin, averaging 18 mU/L and

on two other occasions when they were infused with

insulin at rates that resulted in mean plasma insulin

concentrations of 80 and 150 mU/L They were also

15 A

C

B

D 150

Figure 7.3 The model regulation of glucose metabolism Graphs A, B, C, D Data used in this illustration were obtained from normal

subjects using a series of euglycemic and hyperglycemic clamps at basal or increased insulin concentrations (Sonksen 2001) (A) Total RD (increasing plasma insulin concentration) increases as blood glucose concentration rises but plateaus at higher glucose concentration (B) Total MCR falls with increasing plasma irrespective of the plasma insulin concentration (C, D) Total MCR increases with total RD (increasing plasma insulin concentration) irrespective of the plasma glucose concentration This indicates that increasing insulin concentrations are associated with increasing numbers of glusoce transporters (see text for explanation) Rd, Rate of utilization; Rd1, insulin independent glucose uptake; MCR, metabolic clearance rate Key: x, ○ , ● = different concentrations.

musculoskeletal system, the action is indirect, via the regulation of IGF-1 release.

Sato et al (1986) demonstrated that an increase in glucose metabolism to exogenous insulin in athletes (determined by euglycemic insulin-clamp technique)

was signifi cantly higher than in controls V O2peak was also signifi cantly increased after 1 month’s physi-cal training His data showed that tissue sensitivity to physiological hyper-insulinemia was 46% higher in trained athletes and that physical training improved insulin sensitivity and lipid metabolism

The IR of aging is reversible in older persons (60- to 80-year-olds) It can be decreased by increasing the level of physical training, independent of changes

in weight or body composition (Tonino 1989)

Insulin has effects on protein synthesis and breakdown inmuscle, at concentrations seen after meals (Bennet, Connacher, Scrimgeour et al 1989) Protein synthesis is not performed by insulin but by its regulation of IGF-1 and GH (Bennet, Connacher, Scrimgeour et al 1990)

Its anabolic actions are believed to improve mance by increasing protein synthesis (Bonadonna, Saccomani, Cobelli et al 1993; Kimball et al 1994) and inhibiting protein catabolism and enhancing transport of selected amino acids in human skeletal muscle (Biolo, Fleming, Wolfe et al 1995) Bonadonna

perfor-et al (1993) demonstrated that physiological sulinemia stimulates the activity of amino acid trans-port in human skeletal muscle, thereby stimulating protein synthesis

hyperin-Seven consecutive days of exercise blunted the hyperinsulinemia associated with aging, indepen-dent of any changes in body composition (Cononie, Goldberg, Rogus et al 1994)

Hyperaminoacidemia specifi cally stimulates mus cle protein synthesis and even in the presence of hyperaminoacidemia insulin improves muscle protein balance, solely by inhibiting proteolysis Hyper-aminoacidemia combined with IGF-1 enhances protein synthesis more than either alone (Fryburg et al 1995).Impaired early insulin response and late hyper-insulinemia were predictors of type 2 DM in mid-dle-aged Swedish men (Eriksson, Lindgarde 1996)

-IR preceded glucose intolerance and poor physical

fi tness, as measured by signifi cantly lower V O2peak (16%), signifi cantly lower mean vital capacity (10%), and signifi cantly higher BMI (10%)

Healthy fi rst-degree relatives (FDR) of patients with type 2 DM have a signifi cantly diminished physi-

cal work capacity (determined by V O2peak), ing the argument of a genetic predisposition (Nyholm, Mengel, Nielsen et al 1996) Insulin-treated diabet-ics are known to have increased LBM versus controls (Sinha, Formica, Tsalamandris et al 1996)

support-Insulin induces body weight gain by protecting lean mass, but also leads to fat accumulation in type

technology The shape of the curve suggests simple

“saturation” kinetics obeying Michaelis–Menten

laws

Glucose MCR falls with increasing plasma glucose,

2

independent of the plasma insulin concentration,

in keeping with saturation of the glucose

trans-porter system as plasma glucose rises

MCR increases with increasing plasma insulin

3

concentration, independent of the plasma glucose

concentration This is in keeping with

translo-cation of more glucose transporters into the cell

membrane under the infl uence of increasing

insu-lin concentrations

The parallel nature of the plots shown in

4

Figure 7.3C indicates that increasing insulin

concentrations are associated with increasing

num-ber of “receptors”—in this case, glucose

transport-ers There is no sign of a change in “affnity” of the

transporters under the infl uence of insulin, just

the number present to facilitate glucose entry into

cells (Sonksen 2001)

A cohort of patients referred to a deliberate

self-harm team was asked to complete the HADS

ques-tionnaire The HADS performed well as a screening

instrument; a threshold score of eight gave a

sensitiv-ity of 88% and a positive predictive value of 80% Its

use by non-psychiatrists to detect depressive disorder

in patients presenting with deliberate self-harm has

been recommended (Hamer 1991)

Hart and Frier (1998) retrospectively surveyed 56

admissions, to an urban teaching hospital, of

hypogly-cemic patients in a 12-month period and showed that

80% were diabetics receiving insulin Of these cases,

20% was a consequence of excessive alcohol

consump-tion or deliberate self-poisoning with insulin and had

a history of psychiatric disorder Konrad et al (1998)

discussed the hospital admission of a bodybuilder

taking 70 IU insulin for its anabolic effect but

suffer-ing hypoglycemic convulsions The HADS

question-naire was therefore considered as an appropriate tool

to delineate any psychopathology in this cohort of

drug users and to exclude any possibility of physical

disease

THE EFFECTS OF INSULIN ON

ANTHROPOMETRY AND

EXERCISE PERFORMANCE

Insulin inhibits lipolysis and stimulates lipogenesis

over the same concentration range and is mediated

by the same receptor (Thomas, Wisher, Brandenburg

et al 1979) Hill and Milner (1985) have shown that

insulin is a potent mitogen for many cell types in vitro

They concluded that insulin promotes the growth of

selected tissues by a direct action However, in the

with improvement of the infl ammatory markers CRP and adiponectin (Marcell, McAuley, Traustadottir

et al 2005)

Independent of body fat, BMI, lean mass, and

V O2peak, IR spares muscle glycogen and shifts strate oxidation toward less carbohydrate use (50% lower in the IR vs insulin sensitive [IS] group) and more lipid (28% higher in the IR vs IS group) during exercise (Braun, Sharoff, Chipkin et al 2004) This

sub-may contribute to the decreased V O2peak of sulinemia and the increased cardiovascular risk.Age-related diminution in the composition of skel-etal muscle (SM) mass (sarcopenia), if left untreated, may lead to functional impairment and physical dis-ability The accumulation of lipids within SM fi bers may lead to metabolic disorders such as IR This would appear to correlate with diminution in physi-cal exercise, which accompanies aging (Janssen, Ross 2005)

hyperin-Muscular strength is inversely associated with MS incidence, independent of age and body size in 3233 men over a 23-year period (Jurca, Lamonte, Barlow

et al 2005)

In obese subjects, dynamic strength training improves whole body and adipose tissue responsive-ness It increases responsiveness to the adrenergic β-receptor stimulation of lipolysis and to the antili-polytic action of catecholamines mediated by anti-lipolytic adrenergic α-2A receptors However, there were no training-induced changes in mRNA levels of key genes of the lipolytic pathway in the subcutaneous abdominal adipose tissue (Polak, Moro, Klimcakova

et al 2005)

Strength training is more effective than ance training over a 4-month period in improving gly-cemic control and lipid profi le and may therefore play

endur-a very importendur-ant role in the treendur-atment of type 2 DM (Cauza, Hanusch-Enserer, Strasser et al 2005)

As a consequence of this and similar information being available, bodybuilders and athletes are buying insulin from insulin-dependent diabetics, who get free

“pen-fi lls” paid for by the United Kingdom national health service (NHS) (personal communications) It is possible that the sports individual, who is self-admin-istering exogenous insulin, can be extrapolated to the hyperinsulinemic state with its concomitant metabolic risks It is believed that sportspersons who take insulin may be counseled by physiologists within the scientifi c community, who are not averse to advising their proté-gés on the “emperor’s new clothes.”

THE EFFECTS OF INSULIN

ON BLOOD PRESSURE

Hyperinsulinemia is a major risk factor for rosis and the changes in the vessel wall begin earlier

atheroscle-2 DM (Rigalleau, Delafaye, Baillet et al 1999) In

addition to its role in regulating glucose metabolism,

insulin increases amino acid transport into cells Its

stimulation of lipogenesis and diminished lipolysis,

are reasons why body builders and athletes will take

rhGH in conjunction with insulin, to counteract this

adverse effect while optimizing protein synthesis

(Sonksen, Sonksen 2000; Sonksen 2001)

Insulin modulates transcription, altering the cell

content of numerous mRNAs It stimulates growth,

DNA synthesis, and cell replication Insulin

adminis-tration to uncontrolled diabetics switches off certain

metabolic processes (lipolysis, proteolysis,

ketogen-esis, and gluconeogenesis) (Sonksen 2001) It is the

inhibition of proteolysis that the athlete is interested

in and the physiology of the diabetic patient has

been extrapolated by the “intelligent” athlete to the

sporting arena Insulin increases glucose metabolism

by reducing FFA and ketone levels and recruits more

glucose transporters to the muscle cell membranes,

which facilitates glucose uptake and is refl ected in an

increase of the MCR of glucose (the amount of glucose

cleared from the blood in unit time [mL/kg])

Insulin may enhance performance Primarily, it

stimulates glycogen formation The administration

of exogenous insulin establishes an in vivo

hyperin-sulinemic clamp, increasing muscle glycogen before

and in the recovery stages of strenuous exercise This

increase is believed by the athlete to increase power,

strength, and stamina and assist recovery

Second, by inhibiting muscle protein breakdown

and in conjunction with a

high-protein/high-carbo-hydrate diet, insulin will have the action of increasing

muscle bulk, potentially improving performance

Insulin administration is protein anabolic in

the insulin-resistant state of chronic renal failure

(uremia) It inhibits proteolysis and when

adminis-tered with amino acids increases net protein synthesis

(Lim, Yarasheki, Crowley et al 2003)

Skeletal muscle glucose uptake is higher in trained

men than in untrained men at high relative exercise

intensity, although at lower relative exercise intensities

no differences are observed (Fujimoto, Kemppainen,

Kalliokoski et al 2003)

Elite power athletes appear to be more insulin

resistant than elite endurance athletes (Chou, Lai,

Hsu et al 2005) Chou postulated that such an

indi-vidual may actually benefi t from the effects of

exoge-nous insulin Healthy, insulin-resistant false discovery

rate (FDR) of type 2 DM patients have signifi cantly

enhanced visceral obesity and signifi cantly reduced

V O2peak, compared with people without a family

his-tory of diabetes, despite similar BMI and overall fat

mass (Nyholm, Nielsen, Kristensen et al 2004)

V O2peak is signifi cantly increased in

hyperinsu-linemic insulin-resistant (IR) subjects, as a

conse-quence of exercise training This was not associated