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Endocrine Abstracts (2015) 37 GP18.07 | DOI: 10.1530/endoabs.37.GP.18.07

Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil.


The anterior pituitary gland occupies a central position in the hypothalamus–pituitary glands axes and secretes hormones involved in reproduction, growth, and metabolism. The plasma concentrations of pituitary hormones present fluctuations during the 24 h and are markedly altered during the hypothyroidism. The presence of an intra-pituitary circadian oscillator might be related to these oscillations; however, the molecular mechanism and the consequences of the hypothyroidism are still unknown. The purpose of the present study was to investigate the expression of Bmal1, Per2, Dbp, Nr1d1, Rora, and Dio2 in pituitary during the adult hypothyroidism. For this, euthyroid and thyroidectomized (Tx) male Wistar rats were euthanized during 24 h, every 6 h. The pituitaries were excised and the mRNA expression was evaluated by RT-qPCR. Gapdh and Rpl19 were used as internal control. One and two-way ANOVA, as well as, cosinor analysis were used to evaluate the time-of-day-dependent differential expression for each gene/group and their interactions. The expression of Bmal1, Per2, Dbp, Nr1d1, Rora, and Dio2 presented a circadian pattern in anterior pituitary of euthyroid rats and the peak of Per2, Dpb, Rora, and Dio2 expression occurred at ZT 12, while for Bmal1 was ZT 0/24. In the hypothyroid animals, the circadian pattern of Bmal1, Rora, and Dio2 was lost and the acrophase of Per2, Dbp, and Nr1d1 was advanced about 2.5 h, 3 h, and 45 min respectively. Tx also reduced Mesor values of Dbp and Nr1d1. Our studies reveal that the expression of core clock and clock-controlled genes in anterior pituitary gland are changed during the hypothyroidism and might contribute directly or indirectly to the altered hormonal pattern of secretion observed in this pathological condition. Further studies are in progress to assess this issue.

Disclosure: This work was supported by the FAPESP (2013/05629-4).

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