Thyroxine (thyroid hormone) production

Thyroxine hormone is produced in the thyroid gland from tyrosine and iodine. Thyrotropin-releasing hormone (TRH) is produced by the hypothalamus. It stimulates the production of thyroid-stimulating hormone (TSH) in the anterior pituitary gland, which affects the thyroid-stimulating hormone receptor (TSHR). Iodine is captured by a hydrogen peroxide trap procuced by thyroid peroxidase and added to the 3' and 5' postitions of tyrosine. This can either be free tyrosine or a tyrosine residue in thyroglobuline. After the multiple iodination steps this produces T3 and T4. The production of the thyroid hormones thyroxine (T4),tri-iodothyronine (T3) and reverse T3 (rT3) is dependent on the organification of iodine into thyroglobulin (Tg), the major protein product of the thyroid (2). This involves thyroid peroxidase catalyzed iodination of tyrosine residues in Tg to form mono- and di-iodotyrosines and their subsequent crosslinking to form the iodothyronines T3 and T4. Iodine 131 is an important radioactive fallout product. It was released in the atmosphere after nuclear tests and after nuclear incidents like at Tchernobyl and Fukushima. Since the iodine is concentrated in the thyroid glant as a substrate for the process described here non-radioactive iodine 127 is given as competitor to people exposed.

甲状腺激素甲状腺素由甲状腺从酪氨酸和碘中合成。下丘脑产生的促甲状腺激素释放激素（TRH）刺激垂体前叶分泌促甲状腺激素（TSH），进而影响甲状腺激素受体（TSHR）。碘通过甲状腺过氧化物酶产生的过氧化氢陷阱捕获，并添加到酪氨酸的3'和5'位置。这可以是游离酪氨酸或甲状腺球蛋白中的酪氨酸残基。经过多次碘化步骤后，生成三碘甲状腺原氨酸（T3）和甲状腺素（T4）。甲状腺激素甲状腺素（T4）、三碘甲状腺原氨酸（T3）及逆三碘甲状腺原氨酸（rT3）的生成依赖于碘在甲状腺球蛋白（Tg）中的有机化，甲状腺的主要蛋白质产物（2）。这涉及到甲状腺过氧化物酶催化Tg中酪氨酸残基的碘化，形成单碘酪氨酸和二碘酪氨酸，并随后通过交联形成碘甲状腺原氨酸T3和T4。碘-131是一种重要的放射性沉降物。它是在核试验和类似切尔诺贝利和福岛核事故之后释放到大气中的。由于碘在此过程中作为底物在甲状腺中浓缩，因此向暴露于其中的个体提供非放射性的碘-127作为竞争物。