Growth hormone (GH) effects on bone and collagen turnover in healthy adults and its potential as a marker of GH abuse in sports: a double blind, placebo-controlled study. The GH-2000 Study Group

The Proteomic Signature of Recombinant Growth Hormone in Recreational Athletes

OBJECTIVE

Administration of human growth hormone (hGH) is prohibited in competitive sport and its detection in an athlete's sample triggers an adverse analytical finding. However, the biological processes that are modulated by recombinant hGH are not well characterized and associated blood serum proteins may constitute new biomarkers for hGH misuse.

METHODS

Thirty-five recreational athletes were enrolled in a study to investigate the time- and dose-dependent response of serum protein levels to recombinant hGH administration. Participants were randomly assigned to 4 groups, receiving 1 of 3 different doses of recombinant hGH or a placebo. Bio samples were collected at 22 time points over a period of 13 weeks, starting 4 weeks before treatment, during 3 weeks of treatment, and at 6 weeks' follow-up. A total of 749 serum samples were analyzed for 1305 protein markers using the SOMAscan proteomics platform.

RESULTS

We identified 66 proteins that significantly associated with recombinant hGH administration and dosage, including well known hGH targets, such as IGF1, but also previously unknown hGH-related proteins (eg, protease inhibitors, WFIKKN1, and chemokines, CCL2). Network analysis revealed changes in specific biological pathways, mainly related to the immune system and glucose metabolism.

CONCLUSION

Our analysis suggests that hGH administration affects biological processes more strongly than previously acknowledged. Some of the proteins were dysregulated even after hGH treatment and could potentially be developed into biomarkers for hGH misuse. Moreover, our findings suggest new roles for hGH-associated proteins in the etiology of hGH-related diseases and may indicate new risks that may be associated with hGH misuse.

Transcriptome profiling of insulin sensitive tissues from GH deficient mice following GH treatment

PURPOSE

Most studies that have examined the transcriptional response to GH have been performed with a single tissue. Thus, the current study performed RNASeq across three insulin-sensitive tissues of GH-treated GH deficient (GHKO) mice.

METHODS

GHKO mice were injected with recombinant human GH (hGH) or vehicle daily for 5 days and adipose, liver, and muscle tissues were collected 4 h after the final injection. RNA was isolated from the tissues and sequenced. Genes that were differentially expressed between GH and vehicle treatments were further analyzed. Enrichment analysis and topology-aware pathway analysis were performed.

RESULTS

GHKO mice treated with hGH had expected phenotypic alterations, with increased body, fat, fluid, liver, and muscle mass, and increased serum IGF-1 and insulin. 55 Genes were differentially expressed in all three tissues, including the canonical GH targets Igf1, Igfals, and Cish. Enrichment analysis confirmed the canonical GH response in select tissues, such as cell proliferation, metabolism, and fibrosis. The JAK/STAT pathway was the only pathway significantly altered in all three tissues.

CONCLUSIONS

As expected, GH caused expression changes of many known target genes, although new candidate GH targets were identified. Liver and muscle appear to be more GH sensitive than adipose tissue due to the larger number of DEG and pathways significantly altered, but adipose still has a characteristic GH response. The diversity of changes uncovered in all three tissues after 5 days of GH treatment highlights the multiplicity of GH's effects in its target tissues.

The ElonginB/C-Cullin5-SOCS-Box-Complex Is a Potential Biomarker for Growth Hormone Disorders

Insulin-like growth factor 1 (IGF-1) is the standard biochemical marker for the diagnosis and treatment control of acromegaly and growth hormone deficiency (GHD). However, its limitations necessitate the screening for new specific and sensitive biomarkers. The elonginB/C-cullin5-SOCS-box-complex (ECS-complex) (an intracellular five-protein complex) is stimulated by circulating growth hormone (GH) and regulates GH receptor levels through a negative feedback loop. It mediates the cells' sensitivity for GH and therefore, represents a potent new biomarker for those diseases. In this study, individual ECS-complex proteins were measured in whole blood samples of patients with acromegaly (n = 32) or GHD (n = 12) via ELISA and compared to controls. Hierarchical clustering of the results revealed that by combining the three ECS-complex proteins suppressor of cytokine signaling 2 (SOCS2), cullin-5 and ring-box protein 2 (Rbx-2), 93% of patient samples could be separated from controls, despite many patients having a normal IGF-1 or not receiving medical treatment. SOCS2 showed the best individual diagnostic performance with an overall accuracy of 0.93, while the combination of the three proteins correctly identified all patients and controls. This resulted in perfect sensitivity and specificity for all patient groups, which demonstrates potential benefits of the ECS-complex proteins as clinical biomarkers for the diagnostics of GH-related diseases and substantiates their important role in GH metabolism.

The effect of long-distance running on bone strength and bone biochemical markers

It still remains controversial whether exercise will help or adversely affect the bone formation. The aim of this study was to evaluate the effect of common long-distance running on the magnitude of change in bone properties as measured by quantitative ultrasound (QUS) and bone biochemical markers. Subjects included 68 long-distance runners and 40 controls. Long-distance runners had been training in the marathon club for at least 6 months, the average period of exercise was 2 years, and running at 48.6±24.9 km per week. Otherwise, controls were people who had not experienced any specific sports before. Bone speed of sound (SOS) was measured by QUS at the distal one third radius and the mid-shaft of the tibia. Serum osteocalcin and urine deoxypyridinolin were measured in all groups. No significant differences were found in tibial and radial SOS between the two groups. Serum osteocalcin was higher in long-distance runners than control (P<0.05) in both the 30s and 40s of the participants, but urine deoxypyridinolin showed no significant difference between the two groups. It is concluded that long-distance running at the club level increases bone formation marker, but seems to do no harmful effect on bone properties as measured by QUS.

Increased fibrosis: A novel means by which GH influences white adipose tissue function

OBJECTIVE

White adipose tissue (WAT) fibrosis - the buildup of extracellular matrix (ECM) proteins, primarily collagen - is now a recognized hallmark of tissue dysfunction and is increased with obesity and lipodystrophy. While growth hormone (GH) is known to increase collagen in several tissues, no previous research has addressed its effect on ECM in WAT. Thus, the purpose of this study is to determine if GH influences WAT fibrosis.

DESIGN

This study examined WAT from four distinct strains of GH-altered mice (bGH and GHA transgenic mice as well as two tissue specific GH receptor gene disrupted lines, fat growth hormone receptor knockout or FaGHRKO and liver growth hormone receptor knockout or LiGHRKO mice). Collagen content and adipocyte size were studied in all cohorts and compared to littermate controls. In addition, mRNA expression of fibrosis-associated genes was assessed in one cohort (6month old male bovine GH transgenic and WT mice) and cultured 3T3-L1 adipocytes treated with GH.

RESULTS

Collagen stained area was increased in WAT from bGH mice, was depot-dependent, and increased with age. Furthermore, increased collagen content was associated with decreased adipocyte size in all depots but more dramatic changes in the subcutaneous fat pad. Notably, the increase in collagen was not associated with an increase in collagen gene expression or other genes known to promote fibrosis in WAT, but collagen gene expression was increased with acute GH administration in 3T3-LI cells. In contrast, evaluation of 6month old GH antagonist (GHA) male mice showed significantly decreased collagen in the subcutaneous depot. Lastly, to assess if GH induced collagen deposition directly or indirectly (via IGF-1), fat (Fa) and liver (Li) specific GHRKO mice were evaluated. Decreased fibrosis in FaGHRKO and increased fibrosis in LiGHRKO mice suggest GH is primarily responsible for the alterations in collagen.

CONCLUSIONS

Our results show that GH action is positively associated with an increase in WAT collagen content as well as a decrease in adipocyte size, particularly in the subcutaneous depot. This effect appears to be due to GH and not IGF-1 and reveals a novel means by which GH regulates WAT accumulation.

Growth Hormone Research Society perspective on biomarkers of GH action in children and adults

OBJECTIVE

The Growth Hormone Research Society (GRS) convened a Workshop in 2017 to evaluate clinical endpoints, surrogate endpoints and biomarkers during GH treatment of children and adults and in patients with acromegaly.

PARTICIPANTS

GRS invited 34 international experts including clinicians, basic scientists, a regulatory scientist and physicians from the pharmaceutical industry.

EVIDENCE

Current literature was reviewed and expert opinion was utilized to establish the state of the art and identify current gaps and unmet needs.

CONSENSUS PROCESS

Following plenary presentations, breakout groups discussed questions framed by the planning committee. The attendees re-convened after each breakout session to share the group reports. A writing team compiled the breakout session reports into a document that was subsequently discussed and revised by participants. This was edited further and circulated for final review after the meeting. Participants from pharmaceutical companies were not part of the writing process.

CONCLUSIONS

The clinical endpoint in paediatric GH treatment is adult height with height velocity as a surrogate endpoint. Increased life expectancy is the ideal but unfeasible clinical endpoint of GH treatment in adult GH-deficient patients (GHDA) and in patients with acromegaly. The pragmatic clinical endpoints in GHDA include normalization of body composition and quality of life, whereas symptom relief and reversal of comorbidities are used in acromegaly. Serum IGF-I is widely used as a biomarker, even though it correlates weakly with clinical endpoints in GH treatment, whereas in acromegaly, normalization of IGF-I may be related to improvement in mortality. There is an unmet need for novel biomarkers that capture the pleiotropic actions of GH in relation to GH treatment and in patients with acromegaly.

Growth Hormone's Effect on Adipose Tissue: Quality versus Quantity

Obesity is an excessive accumulation or expansion of adipose tissue (AT) due to an increase in either the size and/or number of its characteristic cell type, the adipocyte. As one of the most significant public health problems of our time, obesity and its associated metabolic complications have demanded that attention be given to finding effective therapeutic options aimed at reducing adiposity or the metabolic dysfunction associated with its accumulation. Growth hormone (GH) has therapeutic potential due to its potent lipolytic effect and resultant ability to reduce AT mass while preserving lean body mass. However, AT and its resident adipocytes are significantly more dynamic and elaborate than once thought and require one not to use the reduction in absolute mass as a readout of efficacy alone. Paradoxically, therapies that reduce GH action may ultimately prove to be healthier, in part because GH also possesses potent anti-insulin activities along with concerns that GH may promote the growth of certain cancers. This review will briefly summarize some of the newer complexities of AT relevant to GH action and describe the current understanding of how GH influences this tissue using data from both humans and mice. We will conclude by considering the therapeutic use of GH or GH antagonists in obesity, as well as important gaps in knowledge regarding GH and AT.

Statistical methodology for age-adjustment of the GH-2000 score detecting growth hormone misuse

Background

The GH-2000 score has been developed as a powerful and unique technique for the detection of growth hormone misuse by sportsmen and women. The score depends upon the measurement of two growth hormone (GH) sensitive markers, insulin-like growth factor-I (IGF-I) and the amino-terminal pro-peptide of type III collagen (P-III-NP). With the collection and establishment of an increasingly large database it has become apparent that the score shows a positive age effect in the male athlete population, which could potentially place older male athletes at a disadvantage.

Methods

We have used results from residual analysis of the general linear model to show that the residual of the GH-2000 score when regressed on the mean-age centred age is an appropriate way to proceed to correct this bias. As six GH-2000 scores are possible depending on the assays used for determining IGF-I and P-III-NP, methodology had to be explored for including six different age effects into a unique residual. Meta-analytic techniques have been utilized to find a summary age effect.

Results

The age-adjusted GH-2000 score, a form of residual, has similar mean and variance as the original GH-2000 score and, hence, the developed decision limits show negligible change when compared to the decision limits based on the original score. We also show that any further scale-transformation will not change the adjusted score. Hence the suggested adjustment is optimal for the given data. The summary age effect is homogeneous across the six scores, and so the generic adjustment of the GH-2000 score formula is justified.

Conclusions

A final revised GH-2000 score formula is provided which is independent of the age of the athlete under consideration.

Developments in our understanding of the effects of growth hormone on white adipose tissue from mice: implications to the clinic

Adipose tissue (AT) is a well-established target of growth hormone (GH) and is altered in clinical conditions associated with excess, deficiency and absence of GH action. Due to the difficulty in collecting AT from clinical populations, genetically modified mice have been useful in better understanding how GH affects this tissue. Recent findings in mice would suggest that the impact of GH on AT is beyond alterations of lipolysis, lipogenesis or proliferation/ differentiation. AT depot-specific alterations in immune cells, extracellular matrix, adipokines, and senescence indicate an expanded role for GH in AT physiology. This mouse data will guide additional studies necessary to evaluate the therapeutic potential and safety of GH for conditions associated with altering AT, such as obesity. In this review, we introduce several relatively new intricacies of GH's effect on AT, focusing on recent studies in mice. Finally, we summarize the clinical implications of these findings.

Identification of biological markers for better characterization of older subjects with physical frailty and sarcopenia

Population aging is rapidly accelerating worldwide; however, longer life expectancy is not the only public health goal. Indeed, extended lifetime involves maintaining function and the capacity of living independently. Sarcopenia and physical frailty are both highly relevant entities with regards to functionality and autonomy of older adults. The concepts and definitions of frailty and sarcopenia have largely been revised over the years. Sarcopenia is an age-related progressive and generalized loss of skeletal muscle mass and strength. On the other hand, frailty is a state of increased vulnerability to stressors, responsible for exposing the older person to enhanced risk of adverse outcomes. Physical frailty and sarcopenia substantially overlap and several adverse outcomes of frailty are likely mediated by sarcopenia. Indeed, the concepts of sarcopenia and physical frailty can be perceived as related to the same target organ (i.e., skeletal muscle) and it may be possible to combine them into a unique definition. The biological background of such a close relationship needs to be explored and clarified as it can potentially provide novel and pivotal insights for the assessment and treatment of these conditions in old age. The aim of this paper is to indicate and discuss possible biological markers to be considered in the framing of physical frailty and sarcopenia.

Multiple protein biomarker assessment for recombinant bovine somatotropin (rbST) abuse in cattle

Biomarker profiling, as a rapid screening approach for detection of hormone abuse, requires well selected candidate biomarkers and a thorough in vivo biomarker evaluation as previously done for detection of growth hormone doping in athletes. The bovine equivalent of growth hormone, called recombinant bovine somatotropin (rbST) is (il)legally administered to enhance milk production in dairy cows. In this study, first a generic sample pre-treatment and 4-plex flow cytometric immunoassay (FCIA) were developed for simultaneous measurement of four candidate biomarkers selected from literature: insulin-like growth factor 1 (IGF-1), its binding protein 2 (IGFBP2), osteocalcin and endogenously produced antibodies against rbST. Next, bovine serum samples from two extensive controlled rbST animal treatment studies were used for in vivo validation and biomarker evaluation. Finally, advanced statistic tools were tested for the assessment of biomarker combination quality aiming to correctly identify rbST-treated animals. The statistical prediction tool k-nearest neighbours using a combination of the biomarkers osteocalcin and endogenously produced antibodies against rbST proved to be very reliable and correctly predicted 95% of the treated samples starting from the second rbST injection until the end of the treatment period and even thereafter. With the same biomarker combination, only 12% of untreated animals appeared false-positive. This reliability meets the requirements of Commission Decision 2002/657/EC for screening methods in veterinary control. From the results of this multidisciplinary study, it is concluded that the osteocalcin - anti-rbST-antibodies combination represent fit-for-purpose biomarkers for screening of rbST abuse in dairy cattle and can be reliably measured in both the developed 4-plex FCIA as well as in a cost-effective 2-plex microsphere-based binding assay. This screening method can be incorporated in routine veterinary monitoring programmes: in the European Union for detection of rbST abuse and in the control of rbST-free dairy farms in the United States of America and other countries.

Differential effects of growth hormone versus insulin-like growth factor-I on the mouse plasma proteome

The GH/IGF-I axis has both pre- and postpubertal metabolic effects. However, the differential effects of GH and/or IGF-I on animal physiology or the plasma proteome are still being unraveled. In this report, we analyzed several physiological effects along with the plasma proteome after treatment of mice with recombinant bovine GH or recombinant human IGF-I. GH and IGF-I showed similar effects in increasing body length, body weight, lean and fluid masses, and organ weights including muscle, kidney, and spleen. However, GH significantly increased serum total cholesterol, whereas IGF-I had no effect on it. Both acute and longer-term effects on the plasma proteome were determined. Proteins found to be significantly changed by recombinant bovine GH and/or recombinant human IGF-I injections were identified by mass spectrometry (MS) and MS/MS. The identities of these proteins were further confirmed by Western blotting analysis. Isoforms of apolipoprotein A4, apolipoprotein E, serum amyloid protein A-1, clusterin, transthyretin, and several albumin fragments were found to be differentially regulated by GH vs. IGF-I in mouse plasma. Thus, we have identified several plasma protein biomarkers that respond specifically and differentially to GH or IGF-I and may represent new physiological targets of these hormones. These findings may lead to better understanding of the independent biological effects of GH vs. IGF-I. In addition, these novel biomarkers may be useful for the development of tests to detect illicit use of GH or IGF-I.

Novel serum protein biomarkers indicative of growth hormone doping in healthy human subjects

The detection of recombinant human growth hormone (rhGH) is difficult due to its short half-life; therefore, novel and robust biomarkers of rhGH abuse are needed. In this study, serum samples derived from subjects treated with rhGH in a randomized, double blind, placebo-controlled crossover study were analyzed by 2-DE coupled with MS. Eight healthy male subjects aged 23.2±0.6 years were injected with rhGH (2 mg/day) or saline for 7 days with serum samples drawn at days 0, 3, and 8. Protein intensities were quantified and analyzed for differences between rhGH and placebo treatments. Proteins that showed significant changes were identified and confirmed by Western blotting. These included specific isoforms of α-1 antitrypsin and transthyretin that increased; and inter-α-trypsin inhibitor heavy chain H4, apolipoprotein A-1, and hemoglobin β chain that decreased. These proteins represent novel biomarkers of short-term rhGH exposure and may lead to a new method for detecting rhGH doping.

Growth hormone doping: a review

The use of growth hormone (GH) as a performance enhancing substance was first promoted in lay publications, long before scientists fully acknowledged its benefits. It is thought athletes currently use GH to enhance their athletic performance and to accelerate the healing of sporting injuries. Over recent years, a number of high profile athletes have admitted to using GH. To date, there is only limited and weak evidence for its beneficial effects on performance. Nevertheless the “hype” around its effectiveness and the lack of a foolproof detection methodology that will detect its abuse longer than 24 hours after the last injection has encouraged its widespread use. This article reviews the current evidence of the ergogenic effects of GH along with the risks associated with its use. The review also examines methodologies, both currently available and in development for detecting its abuse.

Evaluation of early biomarkers of muscle anabolic response to testosterone

BACKGROUND: Early biomarkers of skeletal muscle anabolism will facilitate the development of therapies for sarcopenia and frailty. METHODS AND RESULTS: We examined plasma type III collagen N-terminal propeptide (P3NP), skeletal muscle protein fractional synthesis rate, and gene and protein expression profiles to identify testosterone-induced changes in muscle anabolism. Two placebo-controlled studies enrolled community-dwelling men (study 1, 60-75 years; study 2, 18-40 years) with low to normal testosterone levels. Men were randomized to lower dose (study 1, 100 mg; study 2, 200 mg) or higher dose (study 1, 300 mg; study 2, 600 mg) single intramuscular testosterone or saline injection. After 1 week, testosterone acutely increased plasma P3NP levels in a dose-dependent manner and altered the expression of several skeletal muscle transcripts and proteins. Though not statistically significant, mixed muscle protein fractional synthesis rate tended to increase (1.08-fold with 100 mg testosterone, 1.12-fold with 300 mg testosterone). Testosterone exposure also increased skeletal muscle expression of the collagen type III gene that encodes P3NP. CONCLUSION: P3NP is a potentially useful early biomarker for muscle anabolic therapy. Skeletal muscle protein and RNA profiling are useful tools for the discovery of novel muscle anabolic biomarkers.

From mechanical loading to collagen synthesis, structural changes and function in human tendon

The adaptive response of connective tissue to loading requires increased synthesis and turnover of matrix proteins, with special emphasis on collagen. Collagen formation and degradation in the tendon increases with both acute and chronic loading, and data suggest that a gender difference exists, in that females respond less than males with regard to an increase in collagen formation after exercise. It is suggested that estrogen may contribute toward a diminished collagen synthesis response in females. Conversely, the stimulation of collagen synthesis by other growth factors can be shown in both animal and human models where insulin-like growth factor 1 (IGF-I) and transforming growth factor-beta-1 (TGF-beta-1) expression increases to accompany or precede an increase in procollagen expression and collagen synthesis. In humans, it can be demonstrated that an increase in the interstitial concentration of TGF-beta, PGE2, IGF-I plus its binding proteins and interleukin-6 takes place after exercise. The increase in IGF-I expression in tendon includes the isoform that has so far been thought only to exist in skeletal muscle (mechano growth factor). The increase in IGF-I and procollagen expression showed a similar response whether the tendon was stimulated by concentric, isometric or eccentric muscle contraction, suggesting that strain rather that stress/torque determines the collagen-synthesis stimulating response seen with exercise. The adaptation time to chronic loading is longer in tendon tissue compared with contractile elements of skeletal muscle or the heart, and only with very prolonged loading are significant changes in gross dimensions of the tendon observed, suggesting that habitual loading is associated with a robust change in the size and mechanical properties of human tendons. An intimate interplay between mechanical signalling and biochemical changes in the matrix is needed in tendon, such that chemical changes can be converted into adaptations in the morphology, structure and material properties.

Growth hormone stimulates the collagen synthesis in human tendon and skeletal muscle without affecting myofibrillar protein synthesis

In skeletal muscle and tendon the extracellular matrix confers important tensile properties and is crucially important for tissue regeneration after injury. Musculoskeletal tissue adaptation is influenced by mechanical loading, which modulates the availability of growth factors, including growth hormone (GH) and insulin-like growth factor-I (IGF-I), which may be of key importance. To test the hypothesis that GH promotes matrix collagen synthesis in musculotendinous tissue, we investigated the effects of 14 day administration of 33-50 microg kg(-1) day(-1) recombinant human GH (rhGH) in healthy young individuals. rhGH administration caused an increase in serum GH, serum IGF-I, and IGF-I mRNA expression in tendon and muscle. Tendon collagen I mRNA expression and tendon collagen protein synthesis increased by 3.9-fold and 1.3-fold, respectively (P < 0.01 and P = 0.02), and muscle collagen I mRNA expression and muscle collagen protein synthesis increased by 2.3-fold and 5.8-fold, respectively (P < 0.01 and P = 0.06). Myofibrillar protein synthesis was unaffected by elevation of GH and IGF-I. Moderate exercise did not enhance the effects of GH manipulation. Thus, increased GH availability stimulates matrix collagen synthesis in skeletal muscle and tendon, but without any effect upon myofibrillar protein synthesis. The results suggest that GH is more important in strengthening the matrix tissue than for muscle cell hypertrophy in adult human musculotendinous tissue.

N-terminal propeptide of type III procollagen as a biomarker of anabolic response to recombinant human GH and testosterone

CONTEXT

Biomarkers that predict musculoskeletal response to anabolic therapies should expedite drug development. During collagen synthesis in soft lean tissue, N-terminal propeptide of type III procollagen (P3NP) is released into circulation. We investigated P3NP as a biomarker of lean body mass (LBM) and muscle strength gains in response to testosterone and GH.

DESIGN

Community-dwelling older men received GnRH agonist plus 5 or 10 g testosterone gel plus 0, 3, or 5 microg recombinant human GH daily. P3NP levels were measured at baseline and wk 4, 8, 12, and 16. LBM and appendicular skeletal muscle mass (ASM) were measured by dual-energy x-ray absorptiometry.

RESULTS

One hundred twelve men completed treatment; 106 underwent serum P3NP measurements. P3NP levels were higher at wk 4 than baseline (6.61 +/- 2.14 vs. 4.51 +/- 1.05, P < 0.0001) and reached plateau by wk 4 in men receiving testosterone alone. However, wk 8 P3NP levels were higher than wk 4 levels in men receiving testosterone plus recombinant human GH. Increases in P3NP from baseline to wk 4 and 16 were significantly associated with gains in LBM (r = 0.26, P = 0.007; r = 0.53, P < 0.001) and ASM (r = 0.17, P = 0.07; r = 0.40, P < 0.0001). Importantly, for participants receiving only testosterone, P3NP increases at wk 4 and 16 were related to muscle strength gains (r = 0.20, P = 0.056 and r = 0.36, P = 0.04). In stepwise regression, change in P3NP explained 28 and 30% of the change in ASM and LBM, respectively, whereas change in testosterone but not IGF-I and age provided only small improvements in the models.

CONCLUSION

Early changes in serum P3NP levels are associated with subsequent changes in LBM and ASM during testosterone and GH administration. Serum P3NP may be a useful early predictive biomarker of anabolic response to GH and testosterone.

Perspective: proteomic approach to detect biomarkers of human growth hormone

Several serum biomarkers for recombinant human growth hormone (rhGH) have been established, however, none alone or in combination have generate a specific, sensitive, and reproducible 'kit' for the detection of rhGH abuse. Thus, the search for additional GH specific biomarkers continues. In this review, we focus on the use of proteomics in general and two-dimensional electrophoresis (2-DE) in particular for the discovery of new GH induced serum biomarkers. Also, we review some of the protocols involved in 2-DE. Finally, the possibility of tissues other than blood for biomarker discovery is discussed.

Growth hormone, IGF-I and insulin and their abuse in sport

There is widespread anecdotal evidence that growth hormone (GH) is used by athletes for its anabolic and lipolytic properties. Although there is little evidence that GH improves performance in young healthy adults, randomized controlled studies carried out so far are inadequately designed to demonstrate this, not least because GH is often abused in combination with anabolic steroids and insulin. Some of the anabolic actions of GH are mediated through the generation of insulin-like growth factor-I (IGF-I), and it is believed that this is also being abused. Athletes are exposing themselves to potential harm by self-administering large doses of GH, IGF-I and insulin. The effects of excess GH are exemplified by acromegaly. IGF-I may mediate and cause some of these changes, but in addition, IGF-I may lead to profound hypoglycaemia, as indeed can insulin. Although GH is on the World Anti-doping Agency list of banned substances, the detection of abuse with GH is challenging. Two approaches have been developed to detect GH abuse. The first is based on an assessment of the effect of exogenous recombinant human GH on pituitary GH isoforms and the second is based on the measurement of markers of GH action. As a result, GH abuse can be detected with reasonable sensitivity and specificity. Testing for IGF-I and insulin is in its infancy, but the measurement of markers of GH action may also detect IGF-I usage, while urine mass spectroscopy has begun to identify the use of insulin analogues.

Human growth hormone doping in sport

BACKGROUND AND OBJECTIVES

Recombinant human growth hormone (rhGH) has been on the list of forbidden substances since availability of its recombinant form improved in the early 1990s. Although its effectiveness in enhancing physical performance is still unproved, the compound is likely used for its potential anabolic effect on the muscle growth, and also in combination with other products (androgens, erythropoietin, etc.). The degree of similarity between the endogenous and the recombinant forms, the pulsatile secretion and marked interindividual variability makes detection of doping difficult. Two approaches proposed to overcome this problem are: the indirect method, which measures a combination of several factors in the biological cascade affected by administration of GH; and the direct method, which measures the difference between the circulating and the recombinant (represented by the unique 22 kD molecule) forms of GH. This article gives an overview of what is presently known about hGH in relation to sport. The available methods of detection are also evaluated.

METHODS

Review of the literature on GH in relation to exercise, and its adverse effects and methods of detection when used for doping.

RESULTS AND CONCLUSION

The main effects of exercise on hGH production and the use and effects of rhGH in athletes are discussed. Difficulties encountered by laboratories to prove misuse of this substance by both indirect and direct analyses are emphasised. The direct method currently seems to have the best reliability, even though the time window of detection is too short. hGH doping is a major challenge in the fight against doping. The effect of exercise on hGH and its short half-life are still presenting difficulties during doping analysis. To date the most promising method appears to be the direct approach utilising immunoassays.

Claims for the anabolic effects of growth hormone: a case of the emperor's new clothes?

This review examines the evidence that growth hormone has metabolic effects in adult human beings. The conclusion is that growth hormone does indeed have powerful effects on fat and carbohydrate metabolism, and in particular promotes the metabolic use of adipose tissue triacylglycerol. However, there is no proof that net protein retention is promoted in adults, except possibly of connective tissue. The overexaggeration of the effects of growth hormone in muscle building is effectively promoting its abuse and thereby encouraging athletes and elderly men to expose themselves to increased risk of disease for little benefit.