Endocrinology, Vol 108, 1186-1189, Copyright © 1981 by Endocrine Society

ARTICLES

Effects of fasting on growth hormone secretion in the male baboon

JK Stewart, DJ Koerker, CJ Goodner, CC Gale and RA Steiner

The effects of prolonged fasting on the quantity and pattern of spontaneous GH secretion in 5 adolescent male baboons were investigated. Serum GH concentrations were measured in blood samples taken at 20-min intervals over 12 daytime hours after an overnight fast (control period) and during 84-96 h of fasting. Rhythmic GH secretion, with a mean (+/- SE) period of 5.4 +/- 0.2 h occurred in 4 of the 5 animals in 11 control experiments, and GH peaks occurred randomly in the fifth animal. In response to prolonged fasting, the percent half- amplitude of daytime GH peaks decreased from control values of 144 +/- 12% to 105 +/- 17%. The period of the GH rhythm in 4 animals decreased during fasting, but the change was not statistically significant, and the episodic pattern of GH release in animal 5 was apparently unaffected by fasting. After 84 h of fasting, the mean and integrated concentrations of GH released over 12 daytime hours in the 5 animals were not significantly different from control values. In summary, despite a reduction in GH peak amplitude, the quantity and rhythm of GH secretion were maintained in baboons fasted for 84 h. The observed decrease in GH maxima may play a role in the metabolic adaptation to fasting in the baboon.