Hay I D, Gorman C A, Burman K D, Jiang N S
Metabolism. 1985 Mar;34(3):266-71. doi: 10.1016/0026-0495(85)90011-3.
To compare in man the absorption, serum disappearance, and peripheral monodeiodination of the thyroxine enantiomers, we studied six euthyroid subjects who, on separate occasions, orally ingested 3 mg of either dextrothyroxine (DT4) or levothyroxine (LT4). We measured the serum concentrations of total T4 (TT4), total T3, and reverse T3 (rT3) by nonstereospecific radioimmunoassay and we determined serum DT4 and LT4 by stereospecific chromatography. Mean serum TT4 levels from 4 hours were significantly greater after LT4 administration. After DT4 administration, stereospecific analysis of serum revealed two T4 peaks that persisted from 2 to 48 hours. The mean serum LT4 level did not significantly change during the 48 hours after DT4 administration. Increases in serum T3 and rT3 were seen from 2 hours after administration of either enantiomer. From 12 hours the levels of both triiodothyronines after LT4 were significantly higher than after DT4. In this short term study we found no evidence that in man DT4 is converted to LT4, nor is it preferentially deiodinated to rT3. The greater and more persistent increases in serum T4 and T3 observed after LT4 probably contribute to the known higher bioactivity of that enantiomer.
为了在人体中比较甲状腺素对映体的吸收、血清清除及外周单脱碘作用，我们研究了6名甲状腺功能正常的受试者，他们在不同时间分别口服3mg右旋甲状腺素（DT4）或左旋甲状腺素（LT4）。我们通过非立体特异性放射免疫分析法测定血清总T4（TT4）、总T3和反T3（rT3）的浓度，并通过立体特异性色谱法测定血清DT4和LT4。服用LT4后，4小时起的平均血清TT4水平显著更高。服用DT4后，血清的立体特异性分析显示出两个持续2至48小时的T4峰。在服用DT4后的48小时内，平均血清LT4水平无显著变化。服用任何一种对映体后2小时起，血清T3和rT3升高。从12小时起，服用LT4后的两种三碘甲状腺原氨酸水平显著高于服用DT4后。在这项短期研究中，我们没有发现证据表明在人体中DT4可转化为LT4，也没有发现它优先脱碘生成rT3。服用LT4后观察到的血清T4和T3更大且更持久的升高可能是该对映体已知的更高生物活性的原因。
