Utilisation ergogénique de la somatotropine: Une habitude bien implantée

Abstract

L'utilisation d'agents hypersomatotropinémiants comme aides ergogéniques est un fait bien établi quoique aucune étude documentée n'en fasse mention. La disponibilité de l'hormone de croissance (GH) sur le marché clandestin est favorisée par la production synthétique de l'hormone. Son utilité véritable dans l'amélioration de la performance chez l'athlète adulte reste à être clairement établi; en revanche, les préjudices corporels potentiels le sont: l'acromégalie est le plus insidieux. D'autres pathologies ne peuvent être exclues: diabète sucré, arthrite, myopathies, espérance de vie réduite. Une courte demi-vie et l'impossibilité de distinguer en circulation, tant par des techniques radio-immunologiques (RIA) que radio-immunométriques (IRMA), entre une GH d'origine endogène d'une autre d'origine exogène rendent impossible le dépistage des fraudeurs par les méthodes analytiques conventionnelles. Une nouvelle approche pourrait exploiter l'hétérogénéité fonctionnelle des différentes espèces moléculaires de l'hormone de croissance humaine (hGH). La connaissance des cibles et des actions spécifiques de chacune des espèces moléculaires de hGH pourrait conduire à l'identification de marqueurs secondaires comme, à titre d'exemple, la somatomédine-C, susceptibles de permettre le dépistage des usagers non thérapeutiques de la somatotropine. The problem of misuse of growth hormone as ergogenic aid is of growing concern. Human growth hormone has been recently added to the arsenal of doping agents used in sports principally because of its reported effects on anabolic processes in a variety of tissues, including muscle. In contrast to the problem of anabolic steroid abuse, hGH abuse is a relatively new phenomenon. Reports of its use in athletes are anecdotal. The source of illicit supply is questionable. Until recently, pituitary-extracted hGH was available from different national programs. After the appearance of several cases of Creutzfeldt-Jakob disease, distribution of the product has been halted for an indefinite period. Since withdrawal of the pituitary extracts, recombinant DNA-derived hGH products have been marketed. Soon virtually unlimited quantities will become available, supplies will increase, prices will come down and uses will spread. If pharmacologic benefits are shown to result from use in healthy athletes, GH could become the first genetically-engineered substance available for drug abuse. The economic benefits of tallness in certain sports have encouraged some parents to consider buying the drug for their young athletes. Bogus hGH preparations, animal GH preparations, and foreign products should also be considered as potential illicit sources. To our knowledge, there have been no reports verifying that the GH products bought by athletes are in fact hGH. There is no published evidence of an ergogenic capacitation from GH supplementation. Claims for beneficial effects of GH are numerous, however, especially in weight lifters and bodybuilders. Currently available evidence does not indicate a clear benefit from the use of GH by athletes. Pharmacologic benefits in body-building could arise from low body fat and good muscle definition; its influence in strength and power sports is less certain. There are serious medical problems associated with GH supplementation. Acromegaly is an insidious, irreversible disease that could be of major concern if GH supplementation becomes widespread. Other pathologies cannot be excluded: diabetes mellitus, arthritis, muscle disease, etc. Growth hormone is now listed as an IOC-banned substance; but GH misusers cannot be detected! Short molecular half-life, and inability to differentiate exogenous from endogenous circulating GH molecules allow athletes to avoid detection by current analytical techniques. Improved knowledge of GH physiology appears to be the most promising basis for detection of non-therapeutic users of GH. A new approach could be based on a better appraisal of the physiological properties of the different molecular species of GH; knowledge of body targets and of specificity of action for each molecular forms of GH could lead to the identification of secondary markers (ex. somatomedins) liable to serve as discriminators for ergogenic users.