Growth hormone in sport: beyond Beijing 2008.

Human growth hormone (hGH) is a protein endogenously produced predominantly by the anterior pituitary gland. Native hGH and, especially, its recombinant analogue (rhGH), used to treat patients with hormone deficiency, are supposed to be abused by athletes searching its anabolic and lipolytic effects. Hence, hGH use has been prohibited for a long time by the sport authorities, but until recently, hGH abuse could not be detected. Two approaches have been followed when trying to develop methods for GH abuse detection. The direct method identifies an abnormal ratio between GH isoforms--a result of hGH exogenous administration. The time window to find a cheating athlete by this approach is limited by the excretion time of the hormone. The indirect approach measures serum biomarkers directly affected by GH intake (eg, markers of released liver growth factors and of bone and collagen turnover). In this approach, the retrospective power extends further. Alternative possibilities for cheating related to hGH could be the administration of recombinant growth factors themselves, the administration of hGH metabolic precursors such as ghrelin-like GH secretagogues, or the genetic manipulation of muscle growth-related genes (gene doping). In parallel with the new types of abuse, which will surely emerge in the near future, the research and development for the improvement of the analytical detection of GH itself will continue.