3,5-Diiodothyronine (T2) is on a role. A new hormone in search of recognition

摘要: Thyroid hormone (TH) actions are mediated by triiodothyronine (T3), which acts binding to the TH receptors (TRs). Since exert pleiotropic effects, interest has grown in identifying other possible bioactive thyronines that could explain their diversity of functions. Accordingly, 3,5-diiodothyronine (T2) been shown be bioactive. In mammals, T2 regulates mRNA expression several T3-regulated genes, but doses up 100-fold greater than those T3 were required generate comparable effects. teleosts, and regulate gene vivo with equivalent potency. Furthermore, vitro studies support notion binds activates a specific, long TRβ1 isoform contains nine amino acid insert at beginning ligand domain, whereas can interact also different lacks this insert. Similarly, differentially long- short-TRβ1 expression, respectively, strongly suggesting signaling pathway for each hormone, least species express both receptors. vivo, effectively triggers burst body growth tilapia interacting isoform, supporting is physiologically relevant species. Current knowledge effects action mechanisms lead us propose there an extra level thyroid cascade, produced regulated specifically purpose.