EXERCISE INDUCED RESPONSES OF GROWTH HORMONE, INSULIN-LIKE GROWTH FACTOR-1, AND IGF-BINDING PROTEIN-3 23

Abstract

Listen

Translate article

Insulin-like growth factor-1 (IGF-1) mediates most of the anabolic actions of GH. There is no agreement concerning responses of serum IGF-1 and the major IGF-1 binding protein BP-3 to acute exercise (EX). After exogenous GH administration changes in IGF-1 levels lag more than a few hours. To determine the effect of acute EX on the responses of serum GH. IGF-1 and IGFBP-3. 12 male students (age:19-29 yr) were investigated after an overnight fast. They performed a graded maximal EX test for at least 30 min. on a bicycle ergometer. Venous blood was collected before and immediately after exhaustion, centrifuged directly and stored at -20° C until analysis with specific radio-immunnoassays. Basal GH increased from 9.4 ± 4.5 to 79.8 ± 16.0 mU/l (mean±SEM: Wilcoxon test; p<0.001). No significant differences were observed between pre- and post-EX values of IGF-1 (269.0± 20.8 vs 266.0 ± 17.1 ng/ml), and IGFBP-3 (6.3 ± 0.5 vs 6.0 ± 0.4 mg/l). Basal GH values were positively correlated with basal IGF-1 (r=0.78, p<0.01) and basal IGFBP-3 values (r=0.72, p<0.01). After EX no significant correlations were found between GH, IGF-1 and IGFBP-3. Basal and post-EX values of IGFBP-3 were also not correlated. We conclude that both IGF-1 and IGFBP-3 do not reflect the EX induced massive GH increase and, therefore, are not useful markers to evaluate GH responses to acute EX.