Peptide YY (PYY) sub(3-36) modulates thyrotropin secretion in rats

• Published in: Journal of endocrinology Vol. 191; no. 2; pp. 459 - 463
• Main Authors: Oliveira, K J, Paula, G S M, Costa-e-Sousa, R H, Souza, L L, Moraes, D C, Curty, F H, Pazos-Moura, C C
• Format: Journal Article
• Language: English
• Published: 01-11-2006
• ISSN: 0022-0795; 1479-6805

Peptide YY (PYY) sub(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 sub(3-36) effects on thyrotropin (TSH) secretion, both in vitro and in vivo. PYY sub(3-36)-incubated rat pituitary glands showed a dose-dependent decrease in TSH release, with 44 and 62% reduction at 10 super(-8) and 10 super(-6) M (P < 0.05 and P < 0.001 respectively), and no alteration in TSH response to thyrotropin-releasing hormone. In vivo, PYY sub(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 sub(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 sub(3-36) treatment did not modify significantly serum T sub(4), T sub(3), or leptin. Therefore, in the present paper, we have demonstrated that the gut hormone PYY sub(3-36) acts directly on the pituitary gland to inhibit TSH release, and in the fasting situation, in vivo, when serum PYY sub(3-36) is reduced, the activity of thyroid axis is reduced as well. In such a situation, systemically injected PYY sub(3-36) was able to acutely activate the thyrotrope axis, suggesting a new role for PYY sub(3-36) as a regulator of the hypothalamic-pituitary-thyroid axis.