Growth Hormone Abuse in Athletes

Abstract

Growth hormone (GH) is being used by elite athletes to enhance performance. The rationale appears to come from studies in adults with GH deficiency, where GH replacement has been shown to alter body composition so that lean tis sue mass is increased and fat mass is decreased, to enhance aerobic and resistance performance, to increase cardiac output, to enhance thermal adaptation during exertion, to increase collagen syn thesis, and to modify intermediary metabolism. Documentation of enhanced performance in athletes, however, is currently lacking. Detection of exogenous GH abuse presents a number of unique problems, in that endogenous GH is secreted in a pulsatile fashion and is stimulated by acute exercise. Also, recombinant 22 kDa GH is currently indistinguishable from the endogenous hormone. An international collaborative study group has been established to develop a means of differentiating supra-physiological doses of exogenous GH from endogenous GH secretion in athletes. Current testing strategies center around markers of GH action (the insulin-like growth factor system and markers of bone and collagen turnover), and molecular isoforms of GH. Although additional validation work is required, a test to detect GH abusers can be implemented in the near future.