Correlations of growth hormone (GH) and insulin-like growth factor I (IGF-I): effects of exercise and abuse by athletes

doi:10.1016/S0009-8981(01)00378-3

Clinica Chimica Acta

Volume 305, Issues 1–2, March 2001, Pages 1-17

https://doi.org/10.1016/S0009-8981(01)00378-3 Get rights and content

Abstract

The importance of hormones on body metabolism when physical exercise is carried out has been established for a long time. Growth hormone (GH) is crucial in energy metabolism as well as in body anabolism. Recent studies have increased our knowledge of GH’s mechanisms of action. In particular, insulin-like growth factor I (IGF-I), the main hormone mediating the principal GH effects and other protein structures (i.e. the binding proteins related to these two hormones), has been recognized as playing a crucial role. The biochemical aspects relating to the molecules of the GH/IGF-I axis have been described here. Furthermore, the belief that GH and IGF-I enhance performance has induced an ‘abuse’ of GH (and possibly of IGF-I) by competitive sports athletes and amateurs. The present study outlines the best methods available to uncover abuse, as well as a series of potential research projects to recognize doping. The review also underlines the principal variables measurable in the laboratory and summarizes published reference ranges of these parameters. These biochemical and laboratory profiles describe principal experimental approaches, with the hope that this will stimulate new ideas on the subject of detecting doping practices.

Introduction

Growth hormone (somatotropin) is a polypeptide hormone synthesized and secreted by the somatotroph cells of the anterior pituitary (pituitary growth hormone, pit-GH). Like other protein hormones, it originates from a larger precursor moiety (pro-hormone of the GH, pro-GH), which, although secreted by the pituitary, has no physiological significance. Body growth is the generally known role of this hormone, but, from the biochemical point of view, it also influences the metabolism of proteins, carbohydrates and lipids. Consequently its biochemical actions are multiple, and furthermore most of the growth and metabolic effects are mediated by a peptide hormone, i.e. insulin-like growth factor I (IGF-I) [1]. IGF-I circulates bound to specific proteins (insulin-like growth factor binding proteins, IGFBPs), which regulate its bioavailability and bioactivity.

It is possible that this system plays a role in the body’s adaptive changes to training: thus the concentrations of these molecules in circulation as well as in urine excretion, could be related to body fitness and training. But the firm belief that growth hormone (GH) does enhance performance has led to the ‘abuse’ of GH (and possibly of IGF-I) by competitive athletes. Therefore measurements related to the GH/IGF axis are important not only in defining health but also in doping.

Section snippets

GH/IGF actions and mechanisms

When GH action is discussed, insulin-like growth factors and in particular IGF-I, must also be taken into consideration. In fact the GH/IGF system has physiological and biochemical functions in helping and/or improving performance both in competitions and during training [2]. In addition, GH/IGF-I actions influence fuel compound metabolism such as protein metabolism and body composition [3]. Growth hormone exerts multiple biological actions, initiated by hormone binding to its receptor located

Molecular forms of the GH/IGF system in body fluids

Among the numerous molecules in different body fluids, GH and IGF-I circulating concentrations have probably been studied more than most. But experimental investigation has recently demonstrated that a greater understanding is needed in terms of the analysis of other molecules and other areas such as binding proteins and urine.

Laboratory procedure considerations

The two main assays for the molecules of the GH/IGF system can be divided into receptor assays and immunoassays. The receptor assays are mainly related to GHBP and are measured out by chromatography methods [19], [31]. Immunoassays use hormone/binding protein antibodies. Commercial kits are preferred for routine laboratory analysis. Many of these use polyclonal antibodies, produced against monomeric hormones. However immunoassays, using monoclonal antibodies, are also in use which should allow

Exercise effects

Exercise affects many of the homeostatic mechanisms, with which the endocrine system is intimately involved. There is an increased interest in the endocrine influence on exercise responses. These connections are of particular relevance to the GH/IGF-I axis for several reasons. The physical performance type and time are able to influence GH metabolism, and therefore this GH/IGF-I system, including hormone synthesis, secretion and catabolism, must also be taken into account. The exercise-induced

GH analysis significance for doping control purposes

Immunoassays are usually used in GH and proteins of the GH/IGF system. In Table 3, an outline of the different range values reported in the literature are given. The large circulating GH fluctuation at any time together with the short t_1/2 (10–20 min) of this molecule confers little value to a single GH measurement in assessing GH status. For this reason, clinical studies usually employ physiological or pharmacological tests, performing inhibition or stimulation in the GH secretion. Provocative

Conclusions

The GH/IGF axis must be examined from the physiological and pathological viewpoints as a complex system, in which numerous molecules are involved. The most important of them continue to be the GH and the IGF-I, which are hormones regulating the various biochemical pathways, but probably also their binding proteins. Laboratory analyses are crucial and fundamental approaches. Among the other molecules involved, IGFBP-3, ALS and IGFBP-1 are of particular importance. The metabolism of the GH

Acknowledgements

The authors thank Julia Stevens for her essential help in checking the language of the English text. We would also like to thank CONI, the Federazione Ciclistica Italiana for promoting research in GH investigation and doping.

References (68)

C Chen et al.
The role of receptor dimerization domain residues in growth hormone signaling
J Biol Chem
(1997)
P.E Mullis et al.
Regulation of human growth hormone receptor gene transcription by human growth hormone binding protein
Mol Cell Endocrinol
(1997)
P.F Collett-Solberg et al.
The role of the insulin-like growth factor binding proteins and the IGFBP proteases in modulating IGF action
Endocrinol Metab Clin North Am
(1996)
J.O Johansson et al.
Two weeks of daily injections and continuous infusions of recombinant human growth hormone (GH) in GH-deficient adults. I. Effects on insulin-like growth factor-I (IGF-I), GH and IGF binding proteins, and glucose homeostasis
Metabolism
(1996)
Z Wu et al.
Detection of doping with human growth hormone
Lancet
(1999)
E Shmueli et al.
High insulin-like growth factor binding protein 1 levels in cirrhosis: link with insulin resistance
Hepatology
(1996)
S.G Chadan et al.
Influence of physical activity on plasma insulin-like growth factor-1 and insulin-like growth factor binding proteins in healthy older women
Mech Ageing Dev
(1999)
M Saugy et al.
Detection of human growth hormone doping in urine: out of competition tests are necessary
J Chromatogr B Biomed Sci Appl
(1996)
C.C Lopez Guajardo et al.
Generation, characterization and utilization of anti-human growth hormone 1-43 (hGH1-43) monoclonal antibodies in an ELISA
J Immunol Methods
(1998)
U.J Lewis et al.
A recombinant-DNA-derived modification of human growth hormone (hGH44-191) with enhanced diabetogenic activity
Mol Cell Endocrinol
(1991)

D Le Roith

Insulin-like growth factors

New Eng J Med

(1997)

P.J Jenkins

Growth hormone and exercise

Clin Endocrinol

(1999)

J Rodriguez-Arnao et al.

Effects of growth hormone replacement on physical performance and body composition in GH deficient adults

Clin Endocrinol

(1999)

M Ottosson et al.

Effects of cortisol and growth hormone on lipolysis in human adipose tissue

J Clin Endocrinol Metab

(2000)

J.S Samra et al.

Suppression of the nocturnal rise in growth hormone reduces subsequent lipolysis in subcutaneous adipose tissue

Eur J Clin Invest

(1999)

D.W Leung et al.

Growth hormone receptor and serum binding protein: purification, cloning and expression

Nature

(1987)

E.F De Palo et al.

Influence of physical exercise on growth hormone and its binding protein levels in BCAA treated athletes

J Physiol (Lond)

(1996)

D Turyn et al.

Growth hormone-binding protein enhances growth hormone activity in vivo

Am J Physiol

(1997)

F.S Greenspan et al.

Basic and clinical endocrinology

(1997)

D.A Fryburg et al.

Insulin and insulin-like growth factor-I enhance human skeletal muscle protein anabolism during hyperaminoacidemia by different mechanisms

J Clin Invest

(1995)

G.E Butterfield et al.

Effect of rhGH and rhIGF-I treatment on protein utilization in elderly women

Am J Physiol

(1997)

J.Y Hokama et al.

Voluntary exercise training enhances glucose transport in muscle stimulated by insulin-like growth factor I

J Appl Physiol

(1997)

J.O Jørgensen et al.

Determinants of serum insulin-like growth factor I in growth hormone deficient adults as compared to healthy subjects

Clin Endocrinol (Oxf)

(1998)

J Oscarsson et al.

Diurnal variation in serum insulin-like growth factor (IGF)-I and IGF binding protein-3 concentrations during daily subcutaneous injections of recombinant human growth hormone in GH-deficient adults

Clin Endocrinol (Oxf)

(1997)

R.C Baxter

Insulin-like growth factors and insulin-like growth factor binding protein-3 in the circulation: growth regulators and glucoregulators

Clin Biochem Rev

(1995)

M.C Postel-Vinay

The growth hormone binding protein

J Endocrinol Invest

(1998)

G Baumann

Growth hormone heterogeneity: genes, isohormones, variants, and binding proteins

Endocr Rev

(1991)

G Baumann

Growth hormone heterogeneity in human pituitary and plasma

Horm Res

(1999)

A Eliakim et al.

Physical fitness, endurance training, and the growth hormone-insulin-like growth factor I system in adolescent females

J Clin Endocrinol Metab

(1996)

J.A.M.J.L Janssen et al.

Serum free IGF-I, total IGF-I, IGFBP-1 and IGFBP-3 levels in an elderly population: relation to age and sex steroid levels

Horumon To Rinsho

(1998)

W.F Blum et al.

Serum level of insulin-like growth factor I (IGF-I) and IGF binding protein 3 reflect spontaneous growth hormone secretion

J Clin Endocrinol Metab

(1993)

H Yu et al.

Insulin-like growth factors (IGF-I, free IGF-I, and IGF-II) and insulin-like growth factor binding proteins (IGFBP-2, IGFBP-3, IGFBP-6, and ALS) in blood circulation

J Clin Lab Anal

(1999)

M Westwood et al.

Hormonal regulation of circulating insulin-like growth factor-binding protein-1 phosphorylation status

J Clin Endocrinol Metab

(1995)

R.C Cuneo et al.

Altered endogenous growth hormone secretory kinetics and diurnal GH-binding protein profiles in adults with chronic liver disease

Clin Endocrinol (Oxf)

(1995)

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Due to its considered performance enhancing effects, human growth hormone (hGH) is abused as a doping agent in sport. Its misuse also carries potentially serious side effects to a person’s health. Consequently, hGH and its releasing factors are prohibited in sport, as established in the Prohibited List which is updated and published yearly by the World Anti-Doping Agency (WADA). In order to fight the menace that hGH doping poses to the spirit of sport and to the health of athletes, the sport movement and the anti-doping authorities, initially led by the International Olympic Committee (IOC) and later by WADA, have put substantial efforts into developing tests for its detection. Currently, a primary analytical approach, the isoform differential immunoassay, has been implemented in WADA-accredited laboratories. In parallel, a second, indirect approach for the detection of hGH abuse, based on the quantification of hGH-associated biological markers, has been developed. The final aim is to combine both methodologies to improve the sensitivity and expand the time window to detect doping with hGH. In addition, novel analytical procedures, based on proteomic and genomic technologies as well as the use of mass spectrometry-based methods of detection, are being investigated for future application in hGH anti-doping tests.
Effects of two different types of exercise on GH/IGF axis in athletes. Is the free/total IGF-I ratio a new investigative approach?
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The GH/IGF-I (Growth Hormone/Insulin-like Growth Factor-I) system, together with binding proteins, plays a key role in the adaptation of the organism to exercise. While the GH response to exercise is established [1,2], the IGF-I research demonstrated mixed, non-homogeneous results [3–5]. The discrepancies could be related to differences in the investigated physical exercise (type, duration, intensity), but there are numerous factors which might have an influence, such as body composition, sleep-waking rhythm, nutritional status and energy balance [6–8].
Human growth hormone (hGH) responds to bouts of exercise by increasing, while the insulin-like growth factor-I (IGF-I) responses are conflicting.
Twenty well-trained male cyclists completed a brief duration exercise (A: warm up + increasing workload until exhaustion, lasting 25 min) and a medium duration exercise (B: warm up + 70–80%VO_2 max + increasing workload until exhaustion, lasting 40 min). The immunoreactivity of plasma hGH, the IGF-I in its total and free fraction were measured before and at the end of the exercise, and the free/total IGF-I ratio response to the two cycling exercise bouts was examined.
Both A and B demonstrated increased hGH (from 77 ± 122 to 544 ± 327 and 28 ± 68 to 369 ± 276 pmol/l respectively) and total IGF-I (from 67 ± 10 to 70 ± 10 and 55 ± 14 to 61 ± 15 nmol/l respectively). The free IGF-I was decreased only in A (from 0.38 ± 0.16 to 0.32 ± 0.14 nmol/l). Both A and B demonstrated a decreased free/total IGF-I ratio (from 0.57 ± 0.30 to 0.46 ± 0.22 and 0.61 ± 0.37 to 0.52 ± 0.29).
Brief and medium duration physical exercise influences the hGH, the total and free IGF-I concentrations. The free/total IGF-I ratio was also influenced and it might be related to the GH/IGF system. Its investigation might be a way of studying the training condition.
Enzyme-linked immunosorbent assays for insulin-like growth factor-I using six-histidine tag fused proteins
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It also performs a number of physiological functions, including growth-promoting actions, insulin-like hypoglycemic effects and improvement of glomerular filtration [3–6]. Serum IGF-I is regulated by GH, and the level of IGF-I can be used to indicate GH administration [7–8]. The firm belief that IGF-I and/or GH enhances sports performance has led to its confirmed abuse by competitive athletes.
The fusion proteins of insulin-like growth factor-I (IGF-I) and six-histidine tag (IGF-I-6H, 6H-IGF-I-6H) were cloned, expressed, purified and renatured, with their immunoreaction properties and biological activities intact. The binding kinetics between these fusion proteins and anti-IGF-I antibody or anti-6H antibody were studied using surface plasmon resonance (SPR). Two enzyme-linked immunosorbent assay (ELISA) modes, which proved feasible in the measurement of human serum samples, were used to detect IGF-I with the help of the six-histidine tagged proteins. Furthermore, combining the production technique of the six-histidine tagged fusion protein with the competitive sandwich ELISA mode, using an enzyme labeled anti-6H antibody as a tracer, can be a universal immunochemical method to quantitate other polypeptides or proteins.
Expression and characterization of insulin growth factor-I-enhanced green fluorescent protein fused protein as a tracer for immunoassay
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The firm belief that IGF-I and/or GH does enhance performance has led to the abuse of them by competitive athletes. Although prohibited in sports by the World Anti-Doping Agency, the detection of IGF-I and/or GH abuse poses many challenges [9–11]. There is not yet an approved method to detect IGF-I abuse.
The insulin-like growth factor-I (IGF-I) is an important polypeptide hormone under investigation for body metabolism study and for doping detection. Here, we describe for the first time the expression of a recombinant fusion protein of IGF-I and the enhanced green fluorescent protein (EGFP). The genetic fusion approach enables preparation of conjugates with 1:1 stoichiometry and homogeneous structure. The fused protein (EGFP–IGF-I) was expressed as a soluble protein in cytoplasm of Escherichia coli and its fluorescence and immunoreaction properties were thoroughly characterized. Finally, we demonstrated the utility of the EGFP–IGF-I fusion protein for the fluorescence immunoassay of IGF-1. The linear range of the assay is 1.6 × 10⁻⁸ to 2.0 × 10⁻⁶ M with a detection limit of 1.6 × 10⁻⁸ M. To our knowledge, this is the first time that EGFP has been used as a quantitative label in a fusion protein to develop a quantitative assay for IGF-I. Furthermore, the use of genetically engineered fusion proteins, which combine peptide hormones with fluorescent protein, can lead to a new labeling approach to a number of bioanalytical applications.
Growth hormone isoforms, segments/fragments: Does a link exist with multifunctionality?
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Understanding the relationship between growth hormone (GH) structure (its molecular fragments) and function via interaction with single or multiple receptors is of particular importance in clinical diagnostics and physiologic biochemistry. Direct and indirect actions of GH are numerous ranging from carbohydrate and lipid metabolism to growth effects at muscle and vessels. To this end, we have focused on the influence of physical exercise on GH synthesis and release into the circulation. Physical exercise is a physiological condition to which GH multifunctionality is inextricably linked and is thus important physiologically and pathologically. This review describes the potential human GH fragments with respect to protein hormone multifunctionality and the molecular regions of potential action. The intent of the review is to highlight human GH fragments and hypothesize their potential physiologic role. GH fragmentation is also reviewed in relation to the effects of physical exercise and hormone multifunctionality.
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2005, Trends in Endocrinology and Metabolism
In the past two decades, growth hormone (GH) has been considered as a performance-enhancing drug in the sport world, certainly favoured by the awareness that there is not yet an approved method for detecting its abuse. Because resting or random measurements of plasma GH concentrations per se are meaningless, new methods have been devised to evaluate plasma levels of GH-sensitive substances that are more stable, and hence detectable, than the hormone itself. This review discusses some of the most recently proposed approaches, including a diagnostic algorithm, based on the timed application of different tests, which, collectively, would have a high diagnostic capability.

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ReviewCorrelations of growth hormone (GH) and insulin-like growth factor I (IGF-I): effects of exercise and abuse by athletes

Abstract

Introduction

Section snippets

GH/IGF actions and mechanisms

Molecular forms of the GH/IGF system in body fluids

Laboratory procedure considerations

Exercise effects

GH analysis significance for doping control purposes

Conclusions

Acknowledgements

J Biol Chem

Mol Cell Endocrinol

Endocrinol Metab Clin North Am

Metabolism

Lancet

Hepatology

Mech Ageing Dev

J Chromatogr B Biomed Sci Appl

J Immunol Methods

Mol Cell Endocrinol

Insulin-like growth factors

New Eng J Med

Growth hormone and exercise

Clin Endocrinol

Effects of growth hormone replacement on physical performance and body composition in GH deficient adults

Clin Endocrinol

Effects of cortisol and growth hormone on lipolysis in human adipose tissue

J Clin Endocrinol Metab

Suppression of the nocturnal rise in growth hormone reduces subsequent lipolysis in subcutaneous adipose tissue

Eur J Clin Invest

Growth hormone receptor and serum binding protein: purification, cloning and expression

Nature

Influence of physical exercise on growth hormone and its binding protein levels in BCAA treated athletes

J Physiol (Lond)

Growth hormone-binding protein enhances growth hormone activity in vivo

Am J Physiol

Basic and clinical endocrinology

Insulin and insulin-like growth factor-I enhance human skeletal muscle protein anabolism during hyperaminoacidemia by different mechanisms

J Clin Invest

Effect of rhGH and rhIGF-I treatment on protein utilization in elderly women

Am J Physiol

Voluntary exercise training enhances glucose transport in muscle stimulated by insulin-like growth factor I

J Appl Physiol

Determinants of serum insulin-like growth factor I in growth hormone deficient adults as compared to healthy subjects

Clin Endocrinol (Oxf)

Diurnal variation in serum insulin-like growth factor (IGF)-I and IGF binding protein-3 concentrations during daily subcutaneous injections of recombinant human growth hormone in GH-deficient adults

Clin Endocrinol (Oxf)

Insulin-like growth factors and insulin-like growth factor binding protein-3 in the circulation: growth regulators and glucoregulators

Clin Biochem Rev

The growth hormone binding protein

J Endocrinol Invest

Growth hormone heterogeneity: genes, isohormones, variants, and binding proteins

Endocr Rev

Growth hormone heterogeneity in human pituitary and plasma

Horm Res

Physical fitness, endurance training, and the growth hormone-insulin-like growth factor I system in adolescent females

J Clin Endocrinol Metab

Serum free IGF-I, total IGF-I, IGFBP-1 and IGFBP-3 levels in an elderly population: relation to age and sex steroid levels

Horumon To Rinsho

Serum level of insulin-like growth factor I (IGF-I) and IGF binding protein 3 reflect spontaneous growth hormone secretion

J Clin Endocrinol Metab

Insulin-like growth factors (IGF-I, free IGF-I, and IGF-II) and insulin-like growth factor binding proteins (IGFBP-2, IGFBP-3, IGFBP-6, and ALS) in blood circulation

J Clin Lab Anal

Hormonal regulation of circulating insulin-like growth factor-binding protein-1 phosphorylation status

J Clin Endocrinol Metab

Altered endogenous growth hormone secretory kinetics and diurnal GH-binding protein profiles in adults with chronic liver disease

Clin Endocrinol (Oxf)

Review
Correlations of growth hormone (GH) and insulin-like growth factor I (IGF-I): effects of exercise and abuse by athletes