Growth hormone in sports : is there evidence of benefit?

Despite being banned by the World Anti-Doping Agency, growth hormone (GH) is abused by athletes in sport, reportedly often in combination with anabolic androgenic steroids (AASs). There is evidence for clear benefits of GH treatment for growth hormone deficiency, including normalisation of body composition by increasing lean body mass (LBM) and reducing fat mass due to its lipolytic and anabolic actions, increase in muscle mass but not muscle strength with short-term treatment, and improved aerobic exercise capacity (VO2max). There is only limited evidence available for benefit of GH use in healthy young adults and athletes. GH decreases fat mass and significantly increases LBM in young, healthy physically fit adults. Fluid retention accounts for most of the increase in LBM induced by GH, rather than an increase in the muscle mass. There has been debate as to whether the improved body composition and metabolic changes induced by GH actually translate into improved performance. We have recently demonstrated in a randomised controlled study an increase in anaerobic sprint capacity following treatment with GH for 8 weeks. There is no evidence that GH enhances muscle strength or power, or aerobic exercise capacity in healthy young adults. There is strong evidence of harm from GH abuse. Side effects of GH administration in healthy adults include swelling, arthralgias and paresthesias, fatigue, and changes in cardiac morphology and function. Side effects of GH such as myocardial hypertrophy are likely worsened by co-administration of AASs. The features of acromegaly, including cardiac complications, arthropathy, insulin resistance and increased risk of diabetes and malignancy, indicate potential health risks of chronic GH abuse. In conclusion, the evidence suggests that in healthy adults, GH may improve a selective aspect of performance, that of anaerobic exercise capacity; however, muscle strength, power and aerobic exercise capacity are not enhanced by GH administration. Athletes should be aware of the serious health risks from prolonged use of GH.