There is widespread anecdotal evidence that growth hormone (GH) is used by athletes for its anabolic and lipolytic properties. Although GH is on the World Anti-doping Agency (WADA) 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 the measurement of pituitary GH isoforms and the second is based on the measurement of markers of GH action.Pituitary GH contains multiple isoforms whereas recombinant human GH comprises solely the 22-kDa isoform. Immunoassays that recognize the different isoforms have been developed and form the basis of the test introduced by WADA at the Athens Olympic Games. To date, no athlete has tested positive.The GH-2000 project proposed a test based on the measurement of insulin-like growth factor-I (IGF-I) and type III pro-collagen (P-III-P) as these markers increase in a dose-dependent manner in response to GH and their basal concentration varies much less than GH. When combined with discriminant function analysis, these markers were able to differentiate between those taking GH and placebo in double-blind placebo controlled trials. Subsequent studies have shown that the test is applicable across different ethnicities and is unaffected by injury.