[Molecular mechanism of thyroid hormone synthesis]

Thyroid peroxidase catalyzes the two-electron oxidations of tyrosine and monoiodotyrosine, and one-electron oxidation of diiodotyrosine. This difference in the oxidation, with tyrosine and diiodotyrosine, is also observed in the reaction of thyroid peroxidase with 0.2 and 0.7% iodine thyroglobulins. The results support the hypothesis that the increase in the diiodotyrosine residue in thyroglobulin inhibits further iodination by switching the catalytic cycle to oxidative coupling, to form thyroid hormones. Thyroid hormone synthesis requires iodide, H2O2, thyroglobulin and thyroid peroxidase. The stimulation of iodide uptake and H2O2 generation in the thyroid, as well as, protein synthesis of thyroglobulin and thyroid peroxidase in response to TSH has been reported. The regulation of thyroid hormone synthesis in the thyroid peroxidase reaction and through the peroxidase system is summarized.