Deiodinase

Deiodinase is an enzyme that catalyzes the removal of iodine atoms from thyroxine (T4), a thyroid hormone, to produce triiodothyronine (T3), another thyroid hormone. This process is crucial for regulating metabolism and energy production in the body. There are three main types of deiodinases: type 1 (D1), type 2 (D2), and type 3 (D3), each with distinct functions and tissue distributions.

D1 is primarily found in the liver and kidney, where it converts T4 to T3, which is the more active form of the hormone. D2 is expressed in peripheral tissues such as the heart, muscles, and brown adipose tissue, where it inactivates T4 by converting it to reverse T3 (rT3), which has minimal biological activity. D3 is also expressed in peripheral tissues and is involved in the conversion of T4 to T3 and rT3, with a preference for T4 to T3 conversion.

Deiodinases play a vital role in thyroid hormone homeostasis and are regulated by various factors, including thyroid-stimulating hormone (TSH), retinoic acid, and inflammatory cytokines. Dysregulation of deiodinase activity can lead to metabolic disorders, such as hypothyroidism or hyperthyroidism, and is implicated in the development of obesity, diabetes, and cardiovascular diseases. Therefore, understanding the mechanisms and regulation of deiodinases is essential for the development of therapeutic strategies for these conditions.