Effects of ghrelin, GH-releasing peptide-6 (GHRP-6) and GHRH on GH, ACTH and cortisol release in hyperthyroidism before and after treatment.

In thyrotoxicosis GH responses to stimuli are diminished and the hypothalamic-pituitary-adrenal axis is hyperactive. There are no data on ghrelin or GHRP-6-induced GH, ACTH and cortisol release in treated hyperthyroidism. We, therefore, evaluated these responses in 10 thyrotoxic patients before treatment and in 7 of them after treatment. GHRH-induced GH release was also studied. Peak GH (μg/L; mean ± SE) values after ghrelin (22.6 ± 3.9), GHRP-6 (13.8 ± 2.3) and GHRH (4.9 ± 0.9) were lower in hyperthyroidism before treatment compared to controls (ghrelin: 67.6 ± 19.3; GHRP-6: 25.4 ± 2.7; GHRH: 12.2 ± 2.8) and did not change after 6 months of euthyroidism (ghrelin: 32.7 ± 4.7; GHRP-6: 15.6 ± 3.6; GHRH: 7.4 ± 2.3), although GH responses to all peptides increased in ~50% of the patients. In thyrotoxicosis before treatment ACTH response to ghrelin was two fold higher (107.4 ± 26.3) than those of controls (54.9 ± 10.3), although not significantly. ACTH response to GHRP-6 was similar in both groups (hyperthyroid: 44.7 ± 9.0; controls: 31.3 ± 7.9). There was a trend to a decreased ACTH response to ghrelin after 3 months of euthyroidism (35.6 ± 5.3; P = 0.052), but after 6 months this decrease was non-significant (50.7 ± 14.0). After 3 months ACTH response to GHRP-6 decreased significantly (20.4 ± 4.2), with no further changes. In hyperthyroidism before treatment, peak cortisol (μg/dL) responses to ghrelin (18.2 ± 1.2) and GHRP-6 (15.9 ± 1.4) were comparable to controls (ghrelin: 16.4 ± 1.6; GHRP-6: 13.5 ± 0.9) and no changes were seen after treatment. Our results suggest that the pathways of GH release after ghrelin/GHRP-6 and GHRH are similarly affected by thyroid hormone excess and hypothalamic mechanisms of ACTH release modulated by ghrelin/GHSs may be activated in this situation.
AuthorsPatricia Molica, Sergio Oliva Nascif, Silvia Regina Correa-Silva, Larissa Bianca Paiva Cunha de Sá, José Gilberto Henriques Vieira, Ana-Maria Judith Lengyel
JournalPituitary (Pituitary) Vol. 13 Issue 4 Pg. 315-23 (Dec 2010) ISSN: 1573-7403 [Electronic] United States
PMID20602173 (Publication Type: Clinical Trial, Journal Article, Research Support, Non-U.S. Gov't)
Chemical References
  • Anti-Inflammatory Agents
  • Ghrelin
  • Hormones
  • Oligopeptides
  • growth hormone releasing hexapeptide
  • Adrenocorticotropic Hormone
  • Growth Hormone
  • Growth Hormone-Releasing Hormone
  • Hydrocortisone
  • Adrenocorticotropic Hormone (blood)
  • Adult
  • Anti-Inflammatory Agents (therapeutic use)
  • Female
  • Ghrelin (therapeutic use)
  • Growth Hormone (blood)
  • Growth Hormone-Releasing Hormone (therapeutic use)
  • Hormones (therapeutic use)
  • Humans
  • Hydrocortisone (blood)
  • Male
  • Oligopeptides (therapeutic use)
  • Thyrotoxicosis (blood, drug therapy)

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