Growth hormone receptor antagonist treatment reduces exercise performance in young males

Abstract

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 ( V̇O2max) test and a prolonged exercise test, consisting of 60 min of submaximal cycling followed by exercise to fatigue at 90% of V̇O2max. Main Outcome Measures: V̇O2max 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). V̇O 2max did not change significantly in either group after the treatment period. Time to exhaustion at 90% of V̇O2max 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, V̇O2, 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. Copyright © 2009 by The Endocrine Society.