GROWTH-HORMONE SECRETION IN PUBERTAL AND ADULT SUBJECTS

GH [growth hormone] responsiveness to insulin-induced hypoglycemia and its circadian secretion were studied in a group of subjects in different pubertal stages. The GH peak after insulin was minimal in stage 1 boys (7.6 .+-. 1.3 (SEM [standard error of the mean]) ng/ml) and increased progressively, in parallel with pubertal maturation, reaching a maximum in the adult state (20 .+-. 4.0 ng/ml); the basal value was superimposable in all groups studied. The circadian secretion showed a sleep-related surge which was almost identical in the different stages; in pubertal stage 1 boys multiple secretory peaks were observed, mainly during waking hours. A statistically significant difference (P < 0.05) was observed in the mean concentration recorded during the day with a maximum in stage 1 boys (2.7 .+-. 0.2 ng/ml) and a gradual decrease to a minimum in adults (1.2 .+-. 0.3 ng/ml). This pattern seems to suggest that a pulsatile rhythm is present in boys, similar to that observed for gonadotropins.