Half-time of endogenous growth hormone (GH) disappearance in normal man after stimulation of GH secretion by GH-releasing hormone and suppression with somatostatin.
The half-life (t1/2) of disappearance of endogenous GH from serum was studied using physiological effectors to stimulate and then suppress GH release. GH secretion was stimulated by a single iv injection of GHRH, followed 45 min later by an iv bolus dose and then a 2.5-h infusion of somatostatin (SRIH) to suppress further release. The in vivo t1/2 of GH in seven men was calculated from serum GH concentrations measured at frequent intervals after beginning the SRIH infusion. The mean t1/2 of endogenous GH was 18.9 +/- 0.8 (+/- SE) min by monoexponential analysis and 3.5 +/- 0.7 and 20.7 +/- 0.7 min by biexponential fitting. In these normal men, the decline in GH concentrations after GHRH and SRIH administration was similar to that after the administration of GHRH alone, which yielded a t1/2 of 20.3 +/- 1.9 min. We conclude that the physiological kinetics of endogenous GH removal/disappearance can be estimated in vivo in man using GHRH with or without SRIH infusion.
Faria
A C
AC
Department of Internal Medicine, University of Virginia Medical School, Charlottesville 22908.
Veldhuis
J D
JD
Thorner
M O
MO
Vance
M L
ML
D000328:Adult; D013006:Growth Hormone / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013007:Growth Hormone-Releasing Hormone / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D006207:Half-Life; D006801:Humans; D007262:Infusions, Intravenous; D008297:Male; D013004:Somatostatin / Q000494:pharmacology*
D013004:Somatostatin; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone