The effects of recombinant human insulin-like growth factor-I/Insulin-like growth factor binding protein-3 administration on body composition and physical fitness in recreational athletes

Context:Insulin-like growth factor-I (IGF-I) is thought to mediate many of the anabolic actions of growth hormone (GH) and there are anecdotal reports that IGF-I is misused by elite athletes. There is no published evidence regarding the effects of IGF-I administration on athletic performance.Objective:To investigate the effects of IGF-I administration on body composition and physical fitness in recreational athletes.Design and Setting:Randomised, double-blind, placebo-controlled rhIGF-I/rhIGFBP-3 administration study at Southampton General Hospital, UK.Participants:56 recreational athletes (30 men, 26 women)Intervention:Participants were randomly assigned to receive placebo, low dose rhIGF-I/rhIGFBP-3 (30 mg/day) or high dose rhIGF-I/rhIGFBP-3 (60 mg/day) for 28 days. Body composition (assessed by Dual Energy X-ray Absorptiometry) and cardiorespiratory fitness (assessed by incremental treadmill test), were measured before and immediately after treatment. Within-individual changes after treatment were analysed using paired t-tests.Results:There were no significant changes in body fat mass or lean body mass in women or men after administration of rhIGF-I/rhIGFBP-3 complex. There was a significant increase in maximal oxygen consumption (VO2 max) after treatment. When women and men and low and high dose treatment groups were combined, mean VO2 max increased by approximately 7% (P = 0.001). No significant change in VO2 max was observed in the placebo group.Conclusions:rhIGF-I/rhIGFBP-3 administration for 28 days improves aerobic performance in recreational athletes but there are no effects on body composition.