OCTREOTIDE ADMINISTRATION, UNDER PARTICULAR TEMPORAL CONDITIONS, ENHANCES THE RESPONSES OF GROWTH-HORMONE TO GROWTH HORMONE-RELEASING HORMONE IN NORMAL SUBJECTS

OBJECTIVE Somatostatin not only inhibits basal and GHRH-stimulated GH secretion but might also enhance pituitary GH responsivity to GHRH und er different temporal conditions. We investigated whether octreotide, a long-acting somatostatin analogue, has any positive actions on GHRH- induced GH release in normal human subjects. DESIGN The study consiste d of three protocols. At 0800 hours, after tasting overnight, all subj ects received 1 mu g/kg GHRH i.v. bolus at 0 minutes. In each protocol , either octreotide (200 mu g s.c.) or placebo were given respectively 8, 12, or 16 hours prior to GHRH challenge. SUBJECTS Three groups of eight normal volunteers (four female and four male in each group), age d 18-35 years, were randomly assigned to each protocol. MEASUREMENTS G rowth hormone was measured by IRMA. Samples for GH assay were taken at -30 and 0 minutes and then at 15-minute intervals up to 120 minutes. RESULTS When placebo or octreotide were administered 8 hours before GH RH, peak GH levels were respectively (mean+/-SE, mU/l) 56.2+/-16.6 and 60.8+/-11.4 (NS). Also, when placebo or the somatostatin analogue wer e administered 16 hours prior to GHRH, peak GH levels were comparable (61.0+/-7.4 vs 58.8+/-7.4, NS). However, in the group receiving placeb o or octreotide 12 hours prior to GHRH, the GH responses to GHRH were clearly enhanced by octreotide administration (peak GH levels, mU/l, 5 5.6+/-21.6 vs 104.0+/-17.4, P<0.02). This enhancement of GH responses was observed in all subjects. CONCLUSIONS Octreotide administration di d not affect GH responses to GHRH when given either 8 or 16 hours prio r to GHRH. However, octreotide enhanced GHRH-induced GH release when a dministered 12 hours prior to GHRH. It thus appears that, under partic ular temporal conditions, octreotide may act positively on GH secretio n in man.