Dual and selective actions of glucocorticoids upon basal and stimulated growth hormone release in man

摘要: In humans, corticoids suppress growth and hormone (GH) secretion elicited by a variety of stimuli, while in the rat they potentiate both vivo vitro GH release. To further study this problem, growth-hormone-releasing (GHRH) tests were performed 6 nonobese Cushing’s syndrome patients controls. The normal GHRH-induced was completely abolished group. action shorter corticoid exposures, 34 volunteers subjected to four each: placebo treatment (control); dexamethasone (Dex) administration 4 mg i.v., 3 h before; Dex 8 p.o., 12 before, 22 p.o. over 2 days before pituitary challenge that always administered at 0 min (12.00 h). first test (n = 9), GHRH (1 µg/kg i.v.) induced peak 14.5 ± 3.8 ng/ml (control) potentiated i.v. (26.4 6.8 ng/ml). On contrary, longer treatments values (6.0 1.1 after 1.8 0.3 mg). Clonidine 300 µg 7) increased with an area under secretory curve (AUC) 1,274 236 given clonidine (2,380 489) reduced mg, reduction being significant only Dex(595 47). When arginine 30 g used as 6), (19.1 4.8 ng/ml) AUC (1,318 322) not significanty altered nor but clearly pretreatment (11.1 4.6 peak; 635 189 AUC). rather selective for secretion, because it did alter 6) prolactin, luteinizing follicle-stimulating stimulated combined luteinizing-hormone-releasing thyrotropin-releasing hormone. group, thyrotropin higher (22 mg) treatment. These results showed dual on release man. Short-term basal GHRH-stimulated secretion. stimulatory becomes inhibitory one when are employed, suggesting, though proving, be mediated somatostatin from hypothalamus.