Price D E, O'Malley B P, Northover B, Rosenthal F D
Leicester Royal Infirmary, UK.
Clin Endocrinol (Oxf). 1991 Jul;35(1):67-9. doi: 10.1111/j.1365-2265.1991.tb03498.x.
We have previously reported that, in thyrotoxic patients treated with carbimazole, serum T4 and T3 levels are the first parameters to return to normal, followed by the systolic time interval (STI, a marker of thyroid function at tissue level) and then the serum TSH. The aim of this study was to compare the rate of change of thyroid hormones, TSH and STI in treated hypothyroid patients after the sudden withdrawal of thyroxine.
Serum T4, T3 (free and total) and TSH were measured in 12 patients taking thyroxine for primary hypothyroidism; seven were biochemically euthyroid and five were over-replaced, as defined by an elevated free T4 and a sub-normal TSH. Thyroxine was withdrawn and the measurements repeated three times a week until the STI rose above the euthyroid range (0.26-0.32).
After stopping thyroxine, the serum TSH and STI left the normal range, in advance of the free T4 and T3, after 9.5 +/- 0.95 and 12.2 +/- 1.5 days respectively (mean +/- SEM). The TSH was the first parameter to leave the euthyroid range in all subjects except one in whom the serum TSH was fully suppressed (less than 0.05 mU/l) initially. In the euthyroid group the TSH and STI increased rapidly after stopping thyroxine (time to leave euthyroid range 7.4 +/- 0.8 and 9.4 +/- 0.7 days respectively). In contrast, in the over-replaced group serum TSH and STI became elevated after 12.4 +/- 1.0 days (P less than 0.005 vs euthyroid group) and 16.0 +/- 2.7 days (P less than 0.05 vs euthyroid group) respectively. There was no delay in the fall in serum T4 or T3 in the over-replaced group when compared with the euthyroid group.
In the evolution of primary hypothyroidism, markers of thyroid function at a tissue level (TSH and STI) become abnormal in advance of thyroid hormones. After stopping thyroxine therapy in treated hypothyroid patients, there is a delayed rise in STI and serum TSH levels in subjects with a subnormal TSH level, as compared with those with a normal TSH on treatment. This suggests mild tissue thyrotoxicosis in these individuals.
我们之前曾报道，在接受卡比马唑治疗的甲状腺毒症患者中，血清T4和T3水平是最先恢复正常的参数，其次是收缩时间间期（STI，组织水平甲状腺功能的标志物），然后是血清促甲状腺激素（TSH）。本研究的目的是比较甲状腺激素、TSH和STI在甲状腺素突然停药后接受治疗的甲状腺功能减退患者中的变化率。
对12例因原发性甲状腺功能减退而服用甲状腺素的患者测定血清T4、T3（游离和总）及TSH；7例生化指标甲状腺功能正常，5例甲状腺素替代过量，定义为游离T4升高且TSH低于正常范围。停用甲状腺素，每周重复测量3次，直至STI升至甲状腺功能正常范围（0.26 - 0.32）以上。
停用甲状腺素后，血清TSH和STI分别在9.5±0.95天和12.2±1.5天（均值±标准误）后超出正常范围，早于游离T4和T3。除1例患者最初血清TSH被完全抑制（低于0.05 mU/l）外，TSH是所有受试者中最先超出甲状腺功能正常范围的参数。在甲状腺功能正常组，停用甲状腺素后TSH和STI迅速升高（分别在7.4±0.8天和9.4±0.7天后超出甲状腺功能正常范围）。相比之下，在甲状腺素替代过量组，血清TSH和STI分别在12.4±1.0天（与甲状腺功能正常组相比P<0.005）和16.0±2.7天（与甲状腺功能正常组相比P<0.05）后升高。与甲状腺功能正常组相比，甲状腺素替代过量组血清T4或T3下降无延迟。
在原发性甲状腺功能减退的发展过程中，组织水平的甲状腺功能标志物（TSH和STI）在甲状腺激素之前就出现异常。在接受治疗的甲状腺功能减退患者停用甲状腺素治疗后，与治疗时TSH水平正常的患者相比，TSH水平低于正常的患者STI和血清TSH水平升高延迟。这提示这些个体存在轻度组织性甲状腺毒症。
