Different growth hormone (GH) response to GH-releasing peptide and GH-releasing hormone in hyperthyroidism.

Altered GH responses to several pharmacological stimuli, including GHRH, have been found in hyperthyroidism. The mechanisms underlying these disturbances have not been fully elucidated. GH-releasing peptide-6 (GHRP-6) is a synthetic hexapeptide that specifically stimulates GH release both in vitro and in vivo. The mechanism of action of GHRP-6 is unknown, but it probably acts by inhibiting the effects of somatostatin on GH release. The aim of this study was to evaluate the effects of GHRP-6 on GH secretion in patients with hyperthyroidism (n = 9) and in control subjects (n = 9). Each subject received GHRP-6 (1 microg/kg, iv), GHRH (100 microg, iv), and GHRP-6 plus GHRH on 3 separate days. GH peak values (mean +/- SE; micrograms per L) were significantly lower in hyperthyroid patients compared to those in control subjects after GHRH alone (9.0 +/- 1.3 vs. 27.0 +/- 5.2) and GHRP-6 plus GHRH (22.5 +/- 3.5 vs. 83.7 +/- 15.2); a lack of the normal synergistic effect of the association of both peptides was observed in thyrotoxicosis. However, a similar GH response was seen in both groups after isolated GHRP-6 injection (31.9 +/- 5.7 vs. 23.2 +/- 3.9). In summary, we have shown that hyperthyroid patients have a normal GH response to GHRP-6 together with a blunted GH responsiveness to GHRH. Our data suggest that thyroid hormones modulate GH release induced by these two peptides in a differential way.
AuthorsJ C Ramos-Dias, F Pimentel-Filho, A F Reis, A M Lengyel
JournalThe Journal of clinical endocrinology and metabolism (J Clin Endocrinol Metab) Vol. 81 Issue 4 Pg. 1343-6 (Apr 1996) ISSN: 0021-972X [Print] UNITED STATES
PMID8636330 (Publication Type: Comparative Study, Journal Article, Research Support, Non-U.S. Gov't)
Chemical References
  • Oligopeptides
  • growth hormone releasing hexapeptide
  • Growth Hormone
  • Growth Hormone-Releasing Hormone
  • Adult
  • Analysis of Variance
  • Drug Interactions
  • Female
  • Graves Disease (blood, physiopathology)
  • Growth Hormone (blood, secretion)
  • Growth Hormone-Releasing Hormone (administration & dosage)
  • Humans
  • Injections, Intravenous
  • Kinetics
  • Oligopeptides (administration & dosage)
  • Reference Values
  • Time Factors

Join CureHunter, for free Research Interface BASIC access!

Take advantage of free CureHunter research engine access to explore the best drug and treatment options for any disease. Find out why thousands of doctors, pharma researchers and patient activists around the world use CureHunter every day.
Realize the full power of the drug-disease research network!

Choose Username:
Verify Password: