Liewendahl K, Helenius T, Lamberg B A, Mähönen H, Wägar G
Minerva Foundation Institute, University of Helsinki, Finland.
Acta Endocrinol (Copenh). 1987 Nov;116(3):418-24. doi: 10.1530/acta.0.1160418.
Free thyroxine (FT4) and free triiodothyronine (FT3) concentrations in serum were measured by direct equilibrium dialysis methods in patients receiving thyroxine replacement or suppression therapy. Four of 50 hypothyroid patients euthyroid on replacement therapy (mean thyroxine dose 120 micrograms/day) had supranormal FT4 concentrations, whereas the FT3 concentrations were normal in all. Forty-one of 56 operated thyroid carcinoma patients on suppressive therapy (mean thyroxine dose 214 micrograms/day) had raised FT4 concentrations, whereas the FT3 concentrations was elevated in only one patient. There was a large difference in mean FT4 values for hypothyroid and thyroid carcinoma patients (17.2 vs 29.5 pmol/l), whereas the difference in mean FT3 values was small (5.0 vs 6.1 pmol/l), suggesting a decreased peripheral conversion of T4 to T3 with increasing concentrations of FT4. Serum TSH concentrations, as determined by an immunoradiometric assay, varied from less than 0.02 to 11.9 mU/l in treated hypothyroid patients; 21 patients (42%) had values outside the reference limits. As a single test, serum TSH is therefore not very useful for the assessment of adequate thyroxine dosage in patients with primary hypothyroidism. In thyroid carcinoma patients, the TSH concentrations were less than 0.18 mU/l; 45 patients had values less than 0.02 mU/l indicating sufficient suppression of TSH secretion in the majority of cases. On the basis of these results we recommend the combination of FT3 and TSH tests for monitoring thyroxine replacement and suppression therapy. FT4 appears less useful than FT3 for this purpose even if special reference values values were adopted for each patient group.
采用直接平衡透析法测定接受甲状腺素替代或抑制治疗患者血清中的游离甲状腺素（FT4）和游离三碘甲状腺原氨酸（FT3）浓度。50例接受替代治疗的甲状腺功能减退患者中，有4例甲状腺功能正常（平均甲状腺素剂量为120微克/天），其FT4浓度高于正常水平，而所有患者的FT3浓度均正常。56例接受抑制治疗的甲状腺癌术后患者中，有41例FT4浓度升高（平均甲状腺素剂量为214微克/天），而只有1例患者的FT3浓度升高。甲状腺功能减退患者和甲状腺癌患者的平均FT4值差异很大（17.2对29.5皮摩尔/升），而平均FT3值差异很小（5.0对6.1皮摩尔/升），这表明随着FT4浓度升高，外周血中T4向T3的转化率降低。通过免疫放射分析法测定，接受治疗的甲状腺功能减退患者血清促甲状腺激素（TSH）浓度在低于0.02至11.9毫国际单位/升之间变化；21例患者（42%）的值超出参考范围。因此，作为单一检测指标，血清TSH对于评估原发性甲状腺功能减退患者甲状腺素剂量是否合适并非非常有用。在甲状腺癌患者中，TSH浓度低于0.18毫国际单位/升；45例患者的值低于0.02毫国际单位/升，表明大多数情况下TSH分泌得到了充分抑制。基于这些结果，我们建议联合检测FT3和TSH以监测甲状腺素替代和抑制治疗。即使为每个患者组采用特殊的参考值，FT4在此目的上似乎不如FT3有用。
