The Effects of Growth Hormone on Body Composition and Physical Performance in Recreational Athletes A Randomized Trial Udo Meinhardt, MD; Anne E. Nelson, PhD; Jennifer L. Hansen, RN; Vita Birzniece, MD, PhD; David Clifford, PhD; Kin-Chuen Leung, PhD; Kenneth Graham, BSc; and Ken K.Y. Ho, MD Background: Growth hormone is widely abused by athletes, fre- quently with androgenic steroids. Its effects on performance are unclear. Objective: To determine the effect of growth hormone alone or with testosterone on body composition and measures of performance. Design: Randomized, placebo-controlled, blinded study of 8 weeks of treatment followed by a 6-week washout period. Randomization was computer-generated with concealed allocation. (Australian– New Zealand Clinical Trials Registry registration number: ACTRN012605000508673) Setting: Clinical research facility in Sydney, Australia. Participants: 96 recreationally trained athletes (63 men and 33 women) with a mean age of 27.9 years (SD, 5.7). Intervention: Men were randomly assigned to receive placebo, growth hormone (2 mg/d subcutaneously), testosterone (250 mg/wk intramuscularly), or combined treatments. Women were randomly as- signed to receive either placebo or growth hormone (2 mg/d). Measurements: Body composition variables (fat mass, lean body mass, extracellular water mass, and body cell mass) and physical performance variables (endurance [maximum oxygen consump- tion], strength [dead lift], power [jump height], and sprint capacity [Wingate value]). Results: Body cell mass was correlated with all measures of performance at baseline. Growth hormone significantly re- duced fat mass, increased lean body mass through an increase in extracellular water, and increased body cell mass in men when coadministered with testosterone. Growth hormone sig- nificantly increased sprint capacity, by 0.71 kJ (95% CI, 0.1 to 1.3 kJ; relative increase, 3.9% [CI, 0.0% to 7.7%]) in men and women combined and by 1.7 kJ (CI, 0.5 to 3.0 kJ; relative increase, 8.3% [CI, 3.0% to 13.6%]) when coadmin- istered with testosterone to men; other performance measures did not significantly change. The increase in sprint capacity was not maintained 6 weeks after discontinuation of the drug. Limitations: Growth hormone dosage may have been lower than that used covertly by competitive athletes. The athletic significance of the observed improvements in sprint capacity is unclear, and the study was too small to draw conclusions about safety. Conclusion: Growth hormone supplementation influenced body composition and increased sprint capacity when administered alone and in combination with testosterone. Primary Funding Source: The World Anti-Doping Agency. Ann Intern Med. 2010;152:568-577. www.annals.org For author affiliations, see end of text. A lthough the World Anti-Doping Agency prohibits the use of growth hormone by competitive athletes, illicit use of the drug is widespread (1). The belief that growth hormone enhances performance is based on ob- servations that it increases lean body mass in extremely fit persons (2, 3) and reduces body fat and increases lean mass, fitness, and strength in adults with growth hor- mone deficiency (4). A recent systematic review (3) highlighted the lack of evidence that growth hormone enhances performance. Athletes frequently use growth hormone with androgenic anabolic steroids (5) on the basis of similar beliefs and evidence from studies of el- derly men and men with hypopituitarism that testoster- one enhances the effects of growth hormone on body composition (6). However, we do not know whether the pharmacologic improvements in body composition are associated with improvements in physical performance or whether anabolic steroids enhance the effects of growth hormone in athletes. We previously reported findings (7) from a double- blind, randomized, placebo-controlled trial designed to detect changes in biomarkers (serum insulin-like growth factor [IGF] axis proteins and collagen peptides) in re- sponse to growth hormone administration as part of an effort to develop a test for growth hormone doping. Here, we report findings from prespecified primary anal- yses of secondary outcome data, which we performed to assess how growth hormone changes body composition, whether those changes enhance physical performance, and whether coadministration of testosterone enhances the effects of growth hormone on body composition and performance. See also: Print Editors’ Notes ............................. 569 Summary for Patients ....................... I-44 Web-Only Appendix Appendix Tables Appendix Figures Conversion of graphics into slides Annals of Internal Medicine Article 568 © 2010 American College of Physicians