Nocturnal continuous infusion of growth hormone (gh)-releasing hormone results in a dose-dependent accentuation of episodic gh secretion in normal men

Abstract

Fluctuations in plasma GH levels have been found in patients with acromegaly who have continuously elevated levels of ectopically produced GH-releasing hormone (GHRH). Likewise, plasma GH fluctuations have been found in normal subjects receiving continuous GHRH infusions. We report the effects of two doses of GHRH, administered by constant infusion, on nocturnal GH secretion in six normal young men. Each received, in random order, 2.5 ng/kg-min GHRH, 15 ng/ kg-min GHRH, and 0.15 M NaCl. During both GHRH doses, a highly significant increase in total nocturnal GH secretion was found (P < 0.001) as well as an increase in GH secretion during different periods of the night. Nocturnal GH secretion was episodic during the GHRH infusions, with an increase in the number and magnitude of the peaks compared to those during the NaCl infusion. Plasma immunoreactive GHRH concentrations plateaued at 1 h during the high dose and at 3 h during the low dose GHRH infusion. Sleep parameters, including total sleep time, sleep latency, and duration and timing of the different sleep stages, were not affected by GHRH infusions. We conclude that GHRH, continuously infused, increases nocturnal GH secretion according to the dose, while the episodic pattern of GH secretion is maintained. © 1986 by The Endocrine Society.