Dual and selective actions of glucocorticoids upon basal and stimulated growth hormone release in man.
In humans, corticoids suppress growth and growth hormone (GH) secretion elicited by a variety of stimuli, while in the rat they potentiate both in vivo and in vitro GH release. To further study this problem, growth-hormone-releasing hormone (GHRH) tests were performed in 6 nonobese Cushing's syndrome patients and 6 controls. The normal GHRH-induced GH secretion was completely abolished in the Cushing's syndrome group. To study the action of shorter corticoid exposures, 34 volunteers were subjected to four tests each: placebo treatment (control); dexamethasone (Dex) administration 4 mg i.v., 3 h before; Dex 8 mg p.o., 12 h before, and Dex 22 mg p.o. over the 2 days before the pituitary challenge that was always administered at 0 min (12.00 h). In the first test (n = 9), GHRH (1 microgram/kg i.v.) induced a GH peak of 14.5 +/- 3.8 ng/ml (control) that was potentiated by Dex 4 mg i.v. administered 3 h before (26.4 +/- 6.8 ng/ml). On the contrary, longer Dex treatments suppress GHRH-induced GH values (6.0 +/- 1.1 ng/ml after Dex 8 mg and 1.8 +/- 0.3 ng/ml after Dex 22 mg). Clonidine administration 300 micrograms p.o. (n = 7) increased GH secretion with an area under the secretory curve (AUC) of 1,274 +/- 236 that was potentiated by Dex 4 mg i.v. given 3 h before clonidine (2,380 +/- 489) and reduced by Dex 8 mg, the reduction being significant only after 22 mg Dex (595 +/- 47).(ABSTRACT TRUNCATED AT 250 WORDS)
Burguera
B
B
Department of Medicine, Hospital General Galicia, Santiago de Compostela, Spain.
Muruais
C
C
Peñalva
A
A
Dieguez
C
C
Casanueva
F F
FF
D000328:Adult; D001120:Arginine; D003000:Clonidine; D003480:Cushing Syndrome / Q000378:metabolism*; D003907:Dexamethasone / Q000494:pharmacology*; D005260:Female; D013006:Growth Hormone / Q000378:metabolism*; D013007:Growth Hormone-Releasing Hormone; D006801:Humans; D008297:Male; D008797:Metyrapone; D011388:Prolactin / Q000378:metabolism; D013972:Thyrotropin / Q000378:metabolism; D013973:Thyrotropin-Releasing Hormone
D013973:Thyrotropin-Releasing Hormone; D003907:Dexamethasone; D011388:Prolactin; D013972:Thyrotropin; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone; D001120:Arginine; D003000:Clonidine; D008797:Metyrapone