关键词: HPT轴, 负反馈, 甲状腺激素, 脱碘酶

Abstract: Negative feedback regulation in the hypothalamic-pituitary-thyroid (HPT) axis primarily functions to maintain normal and circulating levels of thyroid hormone (TH). Hypophysiotropic thyrotropin-releasing hormone (TRH) neurons in the paraventricular nucleus (PVN) of the hypothalamus are believed to represent the regulatory core of the HPT axis. Studies have showed that not only circulating triiodothyronine (T3), tetraiodothyronine (T4) could also regulate intracellular T3 availability by type 2 deiodinase (Dio2) in tanycytes and responsible for negative feedback regulation of hypophysiotropic TRH. TH was transported into the hypophysiotropic TRH neurons by TH transporters and bound to thyroid hormone receptors (TRs), especially TRβ2, with the recruitment of coregulators by the TRs, participating in regulation of the corresponding target gene. In addition, tanycytes have been shown to express pyroglutamyl peptidase II (PPII), which degraded TRH releasing from TRH neurons and furthermore affected the TRH concentration in portal blood in different thyroid states. This article summarized molecular components of HPT axis regulation, which was aimed to provide reference for the scientific researches and clinical treatment of thyroid dysfunction or HPT axis abnormalities.

Key words: HPT axis, negative feedback, thyroid hormone, deiodinase