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Laboratório de Endocrinologia Molecular, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21949-900, Brazil

(Requests for offprints should be addressed to C C Pazos-Moura; Email: cpazosm{at}biof.ufrj.br)

Peptide YY (PYY)_3-36 is a gut-derived hormone, with a proposed role in central mediation of postprandial satiety signals, as well as in long-term energy balance. In addition, recently, the ability of the hormone to regulate gonadotropin secretion, acting at pituitary and at hypothalamus has been reported. Here, we examined PYY_3-36 effects on thyrotropin (TSH) secretion, both in vitro and in vivo. PYY_3-36-incubated rat pituitary glands showed a dose-dependent decrease in TSH release, with 44 and 62% reduction at 10^–8 and 10^–6 M (P < 0.05 and P < 0.001 respectively), and no alteration in TSH response to thyrotropin-releasing hormone. In vivo, PYY_3-36 i.p. single injection in the doses of 3 or 30 cg/kg body weight, administered to rats fed ad libitum, was not able to change serum TSH after 15 or 30 min. However, in fasted rats, PYY_3-36 at both doses elicited a significant rise (approximately twofold increase, P < 0.05) in serum TSH observed 15 min after the hormone injection. PYY_3-36 treatment did not modify significantly serum T₄, T₃, or leptin. Therefore, in the present paper, we have demonstrated that the gut hormone PYY_3-36 acts directly on the pituitary gland to inhibit TSH release, and in the fasting situation, in vivo, when serum PYY_3-36 is reduced, the activity of thyroid axis is reduced as well. In such a situation, systemically injected PYY_3-36 was able to acutely activate the thyrotrope axis, suggesting a new role for PYY_3-36 as a regulator of the hypothalamic–pituitary–thyroid axis.

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				M. A. L. C. da Veiga, F. Fonseca Bloise, R. H. Costa-e-Sousa, L. L. Souza, N. A. d. S. Almeida, K. J. Oliveira, and C. C. Pazos-Moura Acute effects of endocannabinoid anandamide and CB1 receptor antagonist, AM251 in the regulation of thyrotropin secretion J. Endocrinol., November 1, 2008; 199(2): 235 - 242. [Abstract] [Full Text] [PDF]