What is the Origin of Thyroid Deiodinases?

The term is derived from the chemical function of the enzymes: "de-" (removal) and "iodine," signifying the removal of an iodine atom. The discovery and characterization of these distinct types in the 1970s and 1980s revolutionized the understanding of thyroid physiology, moving the focus from simple gland secretion to peripheral tissue regulation. This understanding is crucial for diagnosing and managing euthyroid sick syndrome.

What is the Mechanism of Thyroid Deiodinases?

D1 and D2 primarily function to activate T4 into the potent T3, with D2 being particularly important in the brain and pituitary for local T3 supply. Conversely, D3 serves as the primary inactivating enzyme, converting T4 into rT3 and T3 into T2, thereby limiting thyroid hormone action. The coordinated expression and activity of these deiodinases in various tissues allow for precise, local control over metabolic rate, thermogenesis, and neurological development.

Thyroid Deiodinases ∞ Area

Thyroid Deiodinases

Meaning

Thyroid Deiodinases are a family of three selenium-containing enzymes—Deiodinase Type 1 (D1), Type 2 (D2), and Type 3 (D3)—that critically regulate the activation and inactivation of thyroid hormones within target tissues. These enzymes catalyze the removal of iodine atoms from the prohormone thyroxine (T4) to produce the metabolically active triiodothyronine (T3) or the inactive reverse T3 (rT3). They are the ultimate local governors of thyroid hormone action.