Roche J, Michel R
Ann Endocrinol (Paris). 1977 May-Jun;38(3):243-51.
Thirty per cent of the iodine in thyroglobulin is present as iodothyronines. L-thyroxine (T4) represents 90-95% of hormonal iodine, 3,5,3'-triodo-L-thyronine (T3) contains at the most two per cent of it, 3,3'5'-triodo-L-thyronine (rT3) even less, as well as traces of 3,3'-diodo-L-thyronine. The plasma concentration of T4 is about 8 microgram per 100 ml, in the case of T3 it is 120 ng and 25 ng for rT3. The cell nucleus preferentially binds T3 and rT3 and there are also some specific mitochondrial proteins which possess a high affinity for T3. L-thyroxine is dehalogenated peripherically to T3, to take care of most of the requirements in T3. The enrichment of the plasma in rT3 has been shown to occur under various experimental and pathological conditoins. The blood level of T3 varies in inverse ratio to the level of rT3 and it shows that the peripheral formation of one is compensated for by the other. The excess of the prehormone T4 is metabolised as 3,5,3',5'-tetraiodothyroacetic acid (TetrAc); its level in the blood varies in the same way as the level of T3, in particular it decreases during starvation.
甲状腺球蛋白中30%的碘以碘甲状腺原氨酸的形式存在。L-甲状腺素（T4）占激素性碘的90 - 95%，3,5,3'-三碘-L-甲状腺原氨酸（T3）最多占2%，3,3',5'-三碘-L-甲状腺原氨酸（反T3，rT3）占比更少，还有微量的3,3'-二碘-L-甲状腺原氨酸。T4的血浆浓度约为每100毫升8微克，T3为120纳克，反T3为25纳克。细胞核优先结合T3和反T3，也有一些特定的线粒体蛋白对T3具有高亲和力。L-甲状腺素在外周脱卤生成T3，以满足大部分T3的需求。已证实在各种实验和病理条件下血浆中反T3会富集。T3的血药浓度与反T3的浓度成反比，这表明两者在外周的生成是相互代偿的。前激素T4的过量部分代谢为3,5,3',5'-四碘甲状腺乙酸（TetrAc）；其血液水平与T3的变化方式相同，尤其是在饥饿期间会降低。
