The effects of growth hormone on body composition and physical performance in recreational athletes: a randomized trial.
BACKGROUND
Growth hormone is widely abused by athletes, frequently 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.


METHODS
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)


METHODS
Clinical research facility in Sydney, Australia.


METHODS
96 recreationally trained athletes (63 men and 33 women) with a mean age of 27.9 years (SD, 5.7).


METHODS
Men were randomly assigned to receive placebo, growth hormone (2 mg/d subcutaneously), testosterone (250 mg/wk intramuscularly), or combined treatments. Women were randomly assigned to receive either placebo or growth hormone (2 mg/d).


METHODS
Body composition variables (fat mass, lean body mass, extracellular water mass, and body cell mass) and physical performance variables (endurance [maximum oxygen consumption], 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 reduced 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 significantly 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 coadministered 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.


CONCLUSIONS
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.


CONCLUSIONS
Growth hormone supplementation influenced body composition and increased sprint capacity when administered alone and in combination with testosterone.


BACKGROUND
The World Anti-Doping Agency.
Meinhardt
Udo
U
Garvan Institute of Medical Research and St Vincent's Hospital, Darlinghurst, New South Wales, Australia.
Nelson
Anne E
AE
Hansen
Jennifer L
JL
Birzniece
Vita
V
Clifford
David
D
Leung
Kin-Chuen
KC
Graham
Kenneth
K
Ho
Ken K Y
KK
D000273:Adipose Tissue / Q000187:drug effects; D000293:Adolescent; D000328:Adult; D000728:Androgens / Q000009:adverse effects / Q000494:pharmacology*; D054874:Athletic Performance / Q000502:physiology*; D001823:Body Composition / Q000187:drug effects*; D015992:Body Mass Index; D001834:Body Water / Q000187:drug effects; D045604:Extracellular Fluid / Q000187:drug effects; D005260:Female; D019382:Human Growth Hormone / Q000009:adverse effects / Q000494:pharmacology*; D006801:Humans; D008297:Male; D010101:Oxygen Consumption / Q000187:drug effects; D013739:Testosterone / Q000009:adverse effects / Q000494:pharmacology*; D055815:Young Adult
D000728:Androgens; D019382:Human Growth Hormone; D013739:Testosterone