Chopra I J, Williams D E, Orgiazzi J, Solomon D H
J Clin Endocrinol Metab. 1975 Nov;41(5):911-20. doi: 10.1210/jcem-41-5-911.
Dexamethasone, 2 mg every 6 hours for 4 doses, was given to 4 hypothyroid patients receiving treatment with synthetic thyroxine (T4) and to 8 untreated hyperthyroid patients with Graves' disease, and serum concentrations of thyroid hormones were measured by radioimmunoassays. Serum concentration of 3,3'5'-triiodothyronine (reverse T3, rT3) increased appreciably within 8 hours after the first dose of dexamethasone, was maximum at 24-32 hours after beginning dexamethasone, and remained elevated for about 24 hours after discontinuing the steroid. The mean baseline serum rT3 was 58 ng/per 100 ml in treated hypothyroid patients and 119 ng per 100 ml in patients with Graves' disease; the corresponding maximal post-dexamethasone serum rT3 values were 87 and 170 serum concentration of 3,3',5-triiodothyronine (T3) decreased. The decrease in serum T3 was significant at about 24 hours after beginning dexamethasone and was maximal at about 30 hours in both groups of cases under study. The decrease in serum T3 persisted in treated hypothyroid cases for about 24-48 hours and in Graves' disease cases as long as studied, at least 5 days after discontinuing hexamethasone. The changes in serum rT3 and T3 could not be attributed to the effect of dexamethasone on serum protein binding of the iodothyronines because the dialyzable fractions of rT3 and T3 following steroid administration were not different from those before it. Serum T4 did not change appreciably in treated hypothyroid cases, but decreased in Graves' disease cases from a mean baseline value of 23.5 mug per 100 ml to 18.4 mug per 100 ml 3 days after beginning dexamethasone. In addition, 3 hyperthyroid cases were studied before, during, and after administration of dexamethasone, 2 mg every 6 h for 5 days. Serum rT3 increased again as noted above and the increase persisted until about 24 hours after the last dose of the steroid. Serum T3 decreased considerably and remained decreased as long as studied, at least 4 days after discontinuing the steroid. Serum T4 decreased appreciably in 2 of the 3 cases studied. The data suggest that 1) conversion of T4 to T3 and to rT3 may occur via two distinct pathways in the metabolism of T4; 2) the changes in serum rT3 and T3 observed in our study may be due in part at least to a steroid-induced 'shift' in the metabolism of T4 whereby conversion of T4 to T3 is diminished and that to rT3 is enhanced; 3) in addition to the effect on peripheral metabolism of T4, steroids appear to reduce the circulating thyroid hormones in Graves' disease by another mechanism, probably by reduction in thyroid secretion.
对4例接受合成甲状腺素（T4）治疗的甲状腺功能减退患者以及8例未经治疗的格雷夫斯病甲亢患者，给予地塞米松，每6小时2毫克，共4剂，并通过放射免疫分析法测定甲状腺激素的血清浓度。在首次给予地塞米松后8小时内，血清3,3',5'-三碘甲状腺原氨酸（反式T3，rT3）浓度明显升高，在开始使用地塞米松后24 - 32小时达到最高值，并且在停用类固醇后约24小时内仍保持升高。接受治疗的甲状腺功能减退患者的平均基线血清rT3为每100毫升58纳克，格雷夫斯病患者为每100毫升119纳克；地塞米松给药后相应的血清rT3最高值分别为87和170。血清3,3',5-三碘甲状腺原氨酸（T3）浓度降低。在开始使用地塞米松后约24小时，血清T3降低显著，并且在两组研究病例中约30小时时降至最低。在接受治疗的甲状腺功能减退病例中，血清T3的降低持续约24 - 48小时，在格雷夫斯病病例中，只要进行研究，在停用己酸地塞米松后至少5天内一直降低。血清rT3和T3的变化不能归因于地塞米松对碘甲状腺原氨酸血清蛋白结合的影响，因为类固醇给药后rT3和T3的可透析部分与给药前没有差异。在接受治疗的甲状腺功能减退病例中，血清T4没有明显变化，但在格雷夫斯病病例中，在开始使用地塞米松3天后，血清T4从平均基线值每100毫升23.5微克降至18.4微克。此外，对3例甲亢患者在给予地塞米松（每6小时2毫克，共5天）之前、期间和之后进行了研究。血清rT3如上述再次升高，并且这种升高一直持续到最后一剂类固醇后约24小时。血清T3大幅降低，并且只要进行研究，在停用类固醇后至少4天内一直保持降低。在研究中的3例病例中有2例血清T4明显降低。数据表明：1）在T4代谢过程中，T4向T3和rT3的转化可能通过两条不同途径发生；2）我们研究中观察到的血清rT3和T3的变化可能至少部分归因于类固醇诱导的T4代谢“转变”，即T4向T3的转化减少而向rT3的转化增强；3）除了对T4外周代谢的影响外，类固醇似乎通过另一种机制降低格雷夫斯病患者的循环甲状腺激素，可能是通过减少甲状腺分泌。
