Growth hormone receptor antagonist treatment reduces exercise performance in young males

CONTEXT: The effects of GH on exercise performance remain unclear.

OBJECTIVE: The aim of the study was to examine the effects of GH receptor (GHR) antagonist treatment on exercise performance.

DESIGN: Subjects were treated with the GHR antagonist pegvisomant or placebo for 16 d. After the treatment period, they exercised to determine exercise performance and hormonal and metabolic responses.

PARTICIPANTS: Twenty healthy males participated in the study.

INTERVENTION: Subjects were treated with the GHR antagonist (n = 10; 10 mg/d) or placebo (n = 10). After the treatment period, they performed a maximal oxygen uptake (VO(2 max)) test and a prolonged exercise test, consisting of 60 min of submaximal cycling followed by exercise to fatigue at 90% of VO(2 max).

MAIN OUTCOME MEASURES: VO(2 max) was measured before and after the treatment period. Hormonal and metabolic responses and time to exhaustion during prolonged exercise were determined.

RESULTS: Resting serum IGF-I concentration decreased by 20% in the GHR antagonist-treated group (P < 0.05), whereas no change was observed in the placebo group. Conversely, resting serum GH concentration was significantly higher in the treatment group compared with the placebo group (P < 0.01). VO(2 max) did not change significantly in either group after the treatment period. Time to exhaustion at 90% of VO(2 max) was significantly shorter in the treatment group (P < 0.05). No significant differences were observed between the groups in terms of changes in serum free fatty acids, glycerol, VO(2), or relative fat oxidation.

CONCLUSION: GH might be an important determinant of exercise capacity during prolonged exercise, but GHR antagonist did not alter fat metabolism during exercise.