Iodothyronine deiodinase type 1 (DIO1) (DIO1)

Iodothyronine deiodinase type 1 (DIO1) is a selenium-containing enzyme primarily expressed in the liver, kidney, and thyroid gland [UniProt: P41222]. It plays a critical role in thyroid hormone homeostasis by catalyzing both the outer-ring deiodination of thyroxine (T4) to produce the active hormone triiodothyronine (T3) and the inner-ring deiodination of reverse T3 (rT3) into diiodothyronine (T2) [PubMed: 11397876]. While DIO1 contributes significantly to the circulating T3 pool, it is uniquely characterized by its sensitivity to inhibition by thioureylene drugs like propylthiouracil (PTU) [StatPearls: NBK549828]. In clinical practice, DIO1 is a key therapeutic target in the management of severe hyperthyroidism and thyroid storm, where rapid reduction of peripheral T3 is necessary. Drugs such as PTU inhibit DIO1 activity, thereby decreasing the conversion of T4 to T3 and alleviating thyrotoxic symptoms [PubMed: 19035343]. Additionally, DIO1 activity is influenced by selenium status and can be affected by various medications, including amiodarone and certain iodinated contrast agents [PubMed: 21115806]. The enzyme's function is also a factor in non-thyroidal illness syndrome, where its downregulation contributes to the low T3 state observed in systemic illness [PubMed: 25943025].

Other names

Type I iodothyronine deiodinaseType 1 deiodinase5'-deiodinaseD1DIO1Selenoprotein DIO1

Inhibition of the enzyme's catalytic activity, specifically blocking the 5'-deiodination process, to reduce the peripheral conversion of the prohormone thyroxine (T4) into the biologically active triiodothyronine (T3) [StatPearls: NBK549828].