代谢
碘可以通过摄入、吸入或皮肤接触进入人体。在人体内，碘和碘化物会在甲状腺中积累，用于产生甲状腺激素T4和T3。甲状腺中的碘化物会与蛋白质甲状腺球蛋白结合，形成与酪氨酸残基的共价复合物。甲状腺球蛋白的碘化由酶甲状腺过氧化物酶催化。碘化反应发生在甲状腺滤泡细胞-腔界面上，包括碘化物的氧化形成反应中间体，甲状腺球蛋白中单碘酪氨酸和二碘酪氨酸残基的形成，以及碘化酪氨酸残基的耦合形成T4（两个二碘酪氨酸残基的耦合）或T3（一个单碘酪氨酸和一个二碘酪氨酸残基的耦合）。
甲状腺外碘的主要代谢途径涉及T4和T3的分解代谢，包括脱碘反应、甲状腺氨酸醚键的断裂、甲状腺氨酸侧链的氧化脱氨和脱羧，以及甲状腺氨酸上酚羟基与葡萄糖醛酸和硫酸的共轭。吸收的碘主要通过尿液和粪便排出，但也会通过乳汁、呼出气体、汗液和眼泪排出。
Iodine can enter the body following ingestion, inhalaiton, or dermal exposure. In the body, iodine and iodide accumulates in the thyroid gland, where it is used for producing the thyroid hormones T4 and T3. Iodide in the thyroid gland is incorporated into a protein, thyroglobulin, as covalent complexes with tyrosine residues. The iodination of thyroglobulin is catalyzed by the enzyme thyroid peroxidase. The iodination reactions occur at the follicular cell-lumen interface and consist of the oxidation of iodide to form a reactive intermediate, the formation of monoiodotyrosine and diiodotyrosine residues in thyroglobulin, and the coupling of theiodinated tyrosine residues to form T4 (coupling of two diiodotyrosine residues) or T3 (coupling of a monoiodotyrosine and diiodotyrosine residue) in thyroglobulin. The major pathways of metabolism of iodine that occur outside of the thyroid gland involve the catabolism of T4 and T3, and include deiodination reactions, ether bond cleavage of thyronine, oxidative deamination and decarboxylation of the side chain of thyronine, and conjugation of the phenolic hydroxyl group on thyronine with glucuronic acid and sulfate. Absorbed iodine is excreted primarily in the urine and feces, but is also excreted in breast milk, exhaled air, sweat, and tears. (L1844)
来源:Toxin and Toxin Target Database (T3DB)
