Systemic growth hormone does not affect human sleep

Subsequent to sleep onset, GH concentrations increase markedly, suggesting a stimulatory influence of sleep on GH secretion. However, results have been inconsistent as to whether GH conversely exerts a significant influence on sleep. Hence, the effects of exogenous administration of GH and of GH secretion stimulated by GH-releasing hormone (GHRH) on sleep were reexamined in 3 experiments in healthy male volunteers. In Exp I, 12 men participated on 3 experimental nights, receiving a constant iv infusion of 5 IU GH (between 2100-0700 h), an im bolus injection of 5 IU GH at 2100 h, and placebo. In Exp II, the effects of a short iv infusion of a high dose of 48 IU GH (between 2345-2315 h) on sleep were evaluated in 3 men. In Exp III, the effects of continuous infusion of 30 micrograms/h GHRH (between 2200-0700 h) on sleep were compared to the placebo condition in 10 men. Experiments were double blind, within-subject, cross-over comparisons and included an adaptation night before experimental nights. On all nights, the subjects went to bed at 2300 h and were awakened at 0700 h. Administration of GH elevated plasma GH and somatomedin-C levels throughout the night (P < 0.005). Neither im administration of 5 IU GH nor iv administration of 5 and 48 IU GH had any effect on the total sleep time or the time spent in different sleep stages during the whole night or in the first and second halves of sleep time. Infusion of GHRH increased nocturnal GH secretion (P < 0.005), but the episodic pattern of GH secretion was maintained. However, sleep remained unchanged during GHRH infusion. From these results we conclude that in healthy man, systemic GH has no physiological role for sleep regulation.