Journal of Clinical Endocrinology & Metabolism, Vol 69, 1187-1194, Copyright © 1989 by Endocrine Society

ARTICLES

Beta-adrenergic modulation of growth hormone (GH) autofeedback on sleep- associated and pharmacologically induced GH secretion

M Kelijman and LA Frohman
Department of Internal Medicine, University of Cincinnati, College of Medicine, Ohio 45267.

To determine whether GH feedback affects both induced and spontaneous GH secretion and to explore its neurotransmitter mediation, we assessed the effects of 6-h GH infusions (0.55-5.5 micrograms/m2/min) on sleep- associated and GH-releasing hormone (GHRH)-, insulin hypoglycemia-, and arginine-stimulated GH secretion and their modulation by beta- adrenergic blockade in normal men. GH infusions initiated 2 h before the expected onset of sleep produced a dose-dependent inhibition of GH secretion. GH infusions (0.55 micrograms/m2/min) initiated 4 h before the stimuli inhibited the GH response to each, but did not alter the TSH response to TRH. Propranolol infusion (80 micrograms/min) started 2 h before the onset of sleep or the stimulus enhanced GH responses to GHRH and insulin alone and in the presence of GH. In contrast, propranolol neither enhanced the GH responses to arginine or sleep nor reversed the inhibitory effects of GH. The negative feedback effect of GH to both physiological and pharmacological stimuli of GH secretion indicates that it is most likely mediated by both stimulation of somatostatin and inhibition of GHRH release. The effects of beta- adrenergic blockade suggest an inhibition of somatostatin release, although the complex interaction of GH and propranolol implies that they act through dissimilar mechanisms.

This article has been cited by other articles:

				A. Giustina and J. D. Veldhuis Pathophysiology of the Neuroregulation of Growth Hormone Secretion in Experimental Animals and the Human Endocr. Rev., December 1, 1998; 19(6): 717 - 797. [Abstract] [Full Text]