IMR Press / FBL / Volume 25 / Issue 7 / DOI: 10.2741/4857

Frontiers in Bioscience-Landmark (FBL) is published by IMR Press from Volume 26 Issue 5 (2021). Previous articles were published by another publisher on a subscription basis, and they are hosted by IMR Press on imrpress.com as a courtesy and upon agreement with Frontiers in Bioscience.

Open Access Article
Sexually dimorphic dynamics of thyroid axis activity during fasting in rats
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1 Department of Developmental Genetics and Molecular Physiology, Institute of Biotechnology, National University of Mexico (UNAM), Cuernavaca, Mexico
2 Department of Cellular and Molecular Neurobiology, Institute of Neurobiology, National University of Mexico (UNAM), Queretaro, Mexico
3 Laboratory of Molecular Neuroendocrinology, Division of Neuroscience Research, National Institute of Psychiatry, Mexico City, Mexico
Front. Biosci. (Landmark Ed) 2020, 25(7), 1305–1323; https://doi.org/10.2741/4857
Published: 1 March 2020
(This article belongs to the Special Issue Digging deep into thyroid pathophysiology)
Abstract

Starvation induces tertiary hypothyroidism in adult rodents. Response of the hypothalamus-pituitary-thyroid (HPT) axis to starvation is stronger in adult males than in females. To improve the description of this sexual dimorphism, we analyzed the dynamics of HPT axis response to fasting at multiple levels. In adult rats of the same cohort, 24 and 48 h of starvation inhibited paraventricular nucleus Trh expression and serum concentrations of TSH and T4 earlier in males than in females, with lower intensity in females than in males. In adult females fasted for 36-72 h, serum TSH concentration decreased after 36 h, when the activity of thyrotropin-releasing hormone (TRH)-degrading ectoenzyme was increased in the median eminence. The kinetics of these events were distinct from those previously observed in male rats. We suggest that the sex difference in TSH secretion kinetics is driven not only at the level of paraventricular nucleus TRH neurons, but also by differences in post-secretory catabolism of TRH, with enhancement of TRH-degrading activity more sustained in male than female animals.

Keywords
Thyroid
Sex
Fasting
Stress
Thyrotropin
Thyrotropin-releasing hormone
Thyrotropin-releasing hormone-degrading ectoenzyme
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