Local control of thyroid hormone action: role of type 2 deiodinase

Deiodinases: the balance of thyroid hormone

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   Figure 1

   Negative feedback regulation of the hypothalamic–pituitary–thyroid axis. The role of DIO2 in negative feedback control of the HPT axis occurs predominantly in thyrotrophs of the anterior pituitary gland. PVN, para-ventricular nucleus; TRH, thyrotropin-releasing hormone; DIO2, type 2 deiodinase enzyme; TRβ2, thyroid hormone receptor β2; T₄, thyroxine; T₃, 3,5,3′-l-triiodothyronine.
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   Figure 2

   Regulation of intracellular supplies of T₃ to the nucleus of T₃ target cells. MCT8 and MCT10, monocarboxylate transporters 8 and 10; OATP1C1, organic acid transporter protein-1C1; DIO2 and DIO3, type 2 and 3 deiodinase enzymes; TR, thyroid hormone receptor, RXR, retinoid X receptor; T₄, thyroxine; T₃, 3,5,3′-l-triiodothyronine; rT₃, 3,3′,5′-triiodothyronine; T₂, 3,3′-diiodothyronine.

• © 2011 Society for Endocrinology