Suppression of growth hormone (GH) secretion by a selective GH-releasing hormone (GHRH) antagonist. Direct evidence for involvement of endogenous GHRH in the generation of GH pulses.
To study the potential involvement of growth hormone-releasing hormone (GHRH) in the generation of growth hormone (GH) pulses in humans we have used a competitive antagonist to the GHRH receptor, (N-Ac-Tyr1,D-Arg2)GHRH(1-29)NH2(GHRH-Ant). Six healthy young men were given a bolus injection of GHRH-Ant 400 micrograms/kg body wt or vehicle at 2200 h and nocturnal GH concentrations were assessed by every 10-min blood sampling until 0800 h. Integrated total and pulsatile GH secretion were suppressed during GHRH-Ant treatment by 40 +/- 6 (SE) % and 75 +/- 5%, respectively. GHRH-Ant suppressed maximum (7.6 +/- 2.2 vs 1.8 +/- 0.5 micrograms/liter; P < 0.001) and mean (3.3 +/- 1.0 vs 1.1 +/- 0.2 micrograms/liter; P = 0.02) GH pulse amplitudes. There was no change in integrated nonpulsatile GH levels, pulse frequency, or interpulse GH concentration. GHRH-Ant 400 micrograms/kg also suppressed the GH responses to intravenous boluses of GHRH 0.33 micrograms/kg given 1, 6, 12, and 24 h later by 95, 81, 59, and 4%, respectively. In five healthy men, the responses to 10-fold larger GHRH boluses (3.3 micrograms/kg) were suppressed by 82 and 0%, 1 and 6 h after GHRH-Ant 400 micrograms/kg, respectively. These studies provide the first direct evidence that endogenous GHRH participates in the generation of spontaneous GH pulses in humans.
Jaffe
C A
CA
Department of Internal Medicine, Department of Veterans Affairs Medical Center, Ann Arbor, Michigan.
Friberg
R D
RD
Barkan
A L
AL
D000204:Activity Cycles; D000328:Adult; D013006:Growth Hormone / Q000097:blood / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008297:Male; D017337:Sermorelin / Q000031:analogs & derivatives* / Q000494:pharmacology
D017337:Sermorelin; D013006:Growth Hormone; C058677:somatotropin releasing hormone (1-29)amide, N-acetyl-tyrosyl(1)-arginyl(2)-