GH is a peptide hormone and is on the list of substances issued by WADA as banned for competitive sports (5). Until recently, there has been no test available to detect GH abuse; therefore, the prevalence of this abuse can be surmised only through anecdotal evidence.
The performance-enhancing potential of GH for use in sports was first advocated in the Underground Steroid Handbook in 1983 (2), where it was described as "the most expensive, most fashionable and least understood of the new athletic drugs."
After Ben Johnson was stripped his 100-m gold medal from the Seoul Olympic Games, he admitted to having taken a cocktail of drugs including GH. A Chinese swimmer, Yuan Yuan, was forced to withdraw from the 1999 world championship after 13 vials of human GH were discovered in her suitcase. More recently, during a grand jury testimony, Tim Montgomery (former 100-m world record holder) admitted receiving an 8-week supply of GH and a steroid compound known as "the clear" (7).
Both pituitary-derived and short-acting and discontinued depot recombinant human GH (rhGH) are widely available on the internet.
Why Is GH Abused?
There are no clinical trials in healthy humans that demonstrate that GH has a performance-enhancing effect. Nevertheless, anecdotal evidence suggests that GH is widely abused for its anabolic and lipolytic properties.
The anabolic actions of GH are mostly mediated through insulin-like growth factor-I (IGF-I) and include increases in total body protein turnover and muscle synthesis as seen adults with GH deficiency and endurance-trained athletes (8)(9). GH and testosterone act through separate mechanisms and have synergistic effects on anabolism. This has not been lost on athletes, who use cocktails of anabolic agents to gain the maximal effect. GH also stimulates proliferation of cartilage in the growing epiphyseal plate, stimulates linear growth, and increases bone mass, mineral content, and the number of bone-modeling units (10). GH also induces lipolysis in adipose tissue and leads to a reduction in fat mass (11).
The effect of GH is seen most dramatically in adults with GH deficiency in whom treatment with GH leads to increased muscle mass, enhanced use of lipids as a fuel source, improved thermal regulation, increased cardiac output, and improved wound healing and ligamentous strength (11). The replacement of GH for 6 months in adults can lead to an 8.8% increase in muscle mass and 14.4% loss in fat mass (11).
Excess GH secretion also leads to changes in body composition. Patients with active acromegaly have a decreased fat mass and increased lean body mass, both of which are normalized with successful treatment (12). Although most patients with acromegaly do not exhibit athletic prowess, there have been a few cases of athletic achievement in early acromegaly that have provoked debate about the ability of GH to improve performance (13).
Some authors have suggested that the banning of GH is encouraging its use and that future research to develop methodologies to detect its abuse should be stopped (14). These arguments are flawed for several reasons. One reason is that athletes look for an individual response, whereas clinical trials look at mean changes. In addition, similar arguments were made about anabolic steroids, and only recently have clinical trials shown what athletes have known for a long time—anabolic steroids do enhance performance (15). Moreover, research by clinical endocrinologists into the effects of GH has fallen at least a decade behind athletes. Athletes are highly trained to know their performance and evaluate small changes in response to changes in training. By contrast, clinical trials are designed to evaluate relatively large changes. The numbers of study participants needed to detect a 1% change in performance would be huge, whereas the margin for winning an Olympic gold medal is usually less than this. Finally, athletes use a cocktail of drugs that are individually tailored to their requirements. In contrast, clinical trials are designed to evaluate only 1 or 2 interventions at a time with all other variables being kept equal. Athletes therefore provide a new paradigm for examining the potential benefits of new anabolic agents that clinical trials could not, and it is incumbent on us to take note of the agents currently being used.