Iodothyronine deiodinase 1 (DIO1)

Iodothyronine deiodinase 1 (DIO1) is a selenium-dependent enzyme that plays a central role in the peripheral metabolism of thyroid hormones (UniProt P29397). It is primarily expressed in the liver, kidney, and thyroid gland, where it catalyzes both the activation of thyroxine (T4) to the more potent triiodothyronine (T3) and the inactivation of T4 to reverse T3 (rT3) (NCBI Gene 1733). As a major source of circulating T3, DIO1 is a key determinant of thyroid hormone action and basal metabolic rate throughout the body (PubMed 18356288). In conditions such as hyperthyroidism, DIO1 activity is often significantly increased, contributing to elevated T3 levels and clinical thyrotoxicosis (PubMed 21398344). Therapeutic agents like propylthiouracil (PTU) target DIO1 to inhibit the conversion of T4 to T3, providing a critical intervention for managing severe hyperthyroid states and thyroid storm (StatPearls NBK549828). However, the use of such drugs requires careful monitoring due to potential safety concerns, including severe liver injury and agranulocytosis.

Other names

Type I iodothyronine deiodinaseType 1 deiodinaseThyroxine 5-deiodinase type IThyroxine 5'-deiodinase type IIodothyronine 5'-deiodinase type I5DITXDI1THMA2

Inhibition of the conversion of thyroxine (T4) to triiodothyronine (T3) by blocking the 5'-deiodination pathway, thereby reducing the systemic availability of the active thyroid hormone.