Heinen E, Herrmann J, Mosny D, Moreno F, Teschke R, Krüskemper H L
J Endocrinol Invest. 1981 Jul-Sep;4(3):331-4. doi: 10.1007/BF03349453.
An inhibition of peripheral conversion of T4 to T3 is thought to be of benefit in the treatment of thyrotoxicosis. Therefore, propylthiouracil (PTU) has been considered to be more effective in the therapy of hyperthyroidism than methimazole, since the former has the additional peripheral effect of decreasing the conversion of T4 to T3, From in vitro studies PTU is known, however, to inhibit the deiodination at the 5' as well as at the 5 position of the iodothyronine molecule. To study if PTU blocks degradation in T3 in vivo as well, the effect of PTU on thyroid hormone concentrations in serum and liver tissue during a constant and high administration of T4 or T3 to rats was followed. It was shown that PTU clearly inhibits T4 and reverse T3 degradation. Moreover, simultaneous treatment of the rats with T3 and PTU resulted in a significantly higher increase of T3 concentration in liver tissue (11.5 ng/g liver vs 5.6 ng/g liver) and serum (615 ng/di vs 345 ng/dl) than with T3 alone. This effect may be explained by an inhibition of the T3 degradation by PTU in vivo as well. Provided the results obtained from these animal experiments can be applied to the situation in man, the inhibition of peripheral deiodination could have an adverse effect at least in the treatment of T3-thyrotoxicosis.
外周血中甲状腺素（T4）向三碘甲状腺原氨酸（T3）的转化受到抑制被认为对甲状腺毒症的治疗有益。因此，丙硫氧嘧啶（PTU）被认为在甲状腺功能亢进症的治疗中比甲巯咪唑更有效，因为前者具有降低T4向T3转化的额外外周效应。然而，从体外研究可知，PTU可抑制碘甲状腺原氨酸分子5'位和5位的脱碘反应。为了研究PTU在体内是否也会阻断T3的降解，在持续高剂量给大鼠注射T4或T3的过程中，跟踪观察了PTU对血清和肝组织中甲状腺激素浓度的影响。结果表明，PTU能明显抑制T4和反式T3的降解。此外，同时用T3和PTU处理大鼠，肝组织（11.5 ng/g肝组织对5.6 ng/g肝组织）和血清（615 ng/dl对345 ng/dl）中T3浓度的升高幅度明显高于单独使用T3时。这种效应也可能是由于PTU在体内抑制了T3的降解。如果这些动物实验的结果能够应用于人类情况，那么外周脱碘反应的抑制至少在T3型甲状腺毒症的治疗中可能会产生不良影响。
