Growth Hormone and Insulin-Like Growth Factor I Responses to Moderate Submaximal Acute Physical Exercise in Man: Effects of Octreotide, a Somatostatin Analogue, Administration

We evaluated growth hormone (GH) and insulin-like growth factor I (IGF-I) response to moderate submaximal acute short-term physical exercise under basal conditions and after the administration of octreotide, a somatostatin analogue (5A), in a double-blind, counter-balanced experimental protocol. Seven untrained male volunteers performed two identical (exercise tests, each on a treadmill (2.5 % slope) for 30 minutes ((min) at 60 % of VO₂max. Before starting the exercise test all the subjects received a single administration of placebo or octreotide and vice versa at two different sessions. Plasma GH, IGF-I and lactate assays were evaluated before starting, during, at the end and in the recovery phase. In the placebo-treated group GH rose significantly both during exercise and recovery whereas no significant modifications in IGF-I levels were observed. SA administration inhibited the exercise-dependent GH secretion, which showed a small rise only during exercise and returned to basal levels during recovery. In the same group, IGF-I decreased significantly after exercise compared to basal values. The results suggest that 1) in our experimental conditions acute physical exercise at aerobic threshold does not modify IGF-I concentration 2) SA is able to inhibit the exercise-dependent GH secretion and to decrease post-exercise IGF-I concentration.

Key words

Growth hormone - insulin-like growth factor-l - octreotide - physical exercise