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 under 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.


METHODS
The study consisted of three protocols. At 0800 hours, after fasting overnight, all subjects received 1 microgram/kg GHRH i.v. bolus at 0 minutes. In each protocol, either octreotide (200 micrograms s.c.) or placebo were given respectively 8, 12, or 16 hours prior to GHRH challenge.


METHODS
Three groups of eight normal volunteers (four female and four male in each group), aged 18-35 years, were randomly assigned to each protocol.


METHODS
Growth 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 GHRH, 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 were 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 placebo or octreotide 12 hours prior to GHRH, the GH responses to GHRH were clearly enhanced by octreotide administration (peak GH levels, mU/l, 55.6 +/- 21.6 vs 104.0 +/- 17.4, P < 0.02). This enhancement of GH responses was observed in all subjects.


CONCLUSIONS
Octreotide administration did not affect GH responses to GHRH when given either 8 or 16 hours prior to GHRH. However, octreotide enhanced GHRH-induced GH release when administered 12 hours prior to GHRH. It thus appears that, under particular temporal conditions, octreotide may act positively on GH secretion in man.
Valcavi
R
R
2a Divisione di Medicina Interna, Arcispedale S. Maria Nuova, Reggio Emilia, Italy.
Zini
M
M
D000293:Adolescent; D000328:Adult; D004334:Drug Administration Schedule; D004357:Drug Synergism; D005260:Female; D013006:Growth Hormone / Q000097:blood* / Q000187:drug effects; D013007:Growth Hormone-Releasing Hormone / Q000494:pharmacology*; D006801:Humans; D008297:Male; D015282:Octreotide / Q000008:administration & dosage / Q000494:pharmacology*
D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone; D015282:Octreotide