Davies P H, Franklyn J A, Daykin J, Sheppard M C
Department of Medicine, University of Birmingham, Queen Elizabeth Hospital, Edgbaston, United Kingdom.
J Clin Endocrinol Metab. 1992 May;74(5):1189-94. doi: 10.1210/jcem.74.5.1569166.
Use of sensitive assays for TSH in the follow-up of patients treated with radioiodine (131I) for thyrotoxicosis has led to questions regarding the significance of abnormal TSH values found in association with normal circulating thyroid hormone levels, especially TSH results below normal. We have investigated the relationship between serum TSH and the likelihood of maintenance of euthyroidism, as well as the relationship between serum TSH and free T4, in 389 subjects treated with 131I 2-35 years previously who had free T4 and free T3 values within the normal range and who were not receiving thyroxine or antithyroid therapy. In those with undetectable TSH (less than 0.05 mU/L), TSH remained undetectable in 54.5% at 1 yr but rose to detectable or normal values in the remainder. In those with low but measurable TSH (0.05-0.5 mU/L), results were similar at 1 yr in 47.5% and returned to normal in 45%. No patient with a TSH value below normal became hypothyroid (defined as a reduction in serum free T4). In those with normal TSH (0.5-5.0 mU/L) at time 0, TSH remained normal in 83%, fell in 4% and became elevated in 13%. The yr 1 incidence of hypothyroidism was 1%; one patient became thyrotoxic. In those with TSH values above normal (5.0-15.0 mU/L), TSH remained elevated in 90.6%; the incidence of hypothyroidism was 14.5% in yr 1. The small risk of development of hypothyroidism in those with subnormal or normal TSH indicates that biochemical testing is not essential for 1-2 yr in such patients; this contrasts with a need for repeat testing within a period not exceeding 1 yr in those with elevated TSH. The relationship between serum-free T4 and TSH suggests that TSH results outside the normal range reflect thyroid hormone excess or deficiency. Persistence of undetectable TSH values during follow-up and the observation of higher free T4 at time 0 in those whose TSH remained undetectable compared with those whose TSH rose suggest that undetectable TSH concentrations are of greater significance than low but detectable values.
在对因甲状腺毒症接受放射性碘（131I）治疗的患者进行随访时，使用敏感的促甲状腺激素（TSH）检测方法引发了一些问题，即与正常循环甲状腺激素水平相关的异常TSH值的意义，尤其是低于正常的TSH结果。我们研究了389名在2至35年前接受过131I治疗的受试者中血清TSH与维持甲状腺功能正常可能性之间的关系，以及血清TSH与游离T4之间的关系。这些受试者的游离T4和游离T3值在正常范围内，且未接受甲状腺素或抗甲状腺治疗。在TSH检测不到（低于0.05 mU/L）的患者中，1年后54.5%的患者TSH仍检测不到，但其余患者的TSH升至可检测或正常水平。在TSH低但可测量（0.05 - 0.5 mU/L）的患者中，47.5%的患者1年后结果相似，45%的患者恢复正常。TSH值低于正常的患者均未出现甲状腺功能减退（定义为血清游离T4降低）。在初始时TSH正常（0.5 - 5.0 mU/L）的患者中，83%的患者TSH仍保持正常，4%的患者TSH下降，13%的患者TSH升高。第1年甲状腺功能减退的发生率为1%；1名患者出现甲状腺毒症。在TSH值高于正常（5.0 - 15.0 mU/L）的患者中，90.6%的患者TSH仍升高；第1年甲状腺功能减退的发生率为14.5%。TSH低于正常或正常的患者发生甲状腺功能减退的风险较小，这表明在此类患者中1至2年内进行生化检测并非必要；这与TSH升高的患者需要在不超过1年的时间内进行重复检测形成对比。血清游离T4与TSH之间的关系表明，超出正常范围的TSH结果反映了甲状腺激素过多或不足。随访期间TSH检测不到值的持续存在，以及与TSH升高的患者相比，TSH仍检测不到的患者在初始时游离T4较高的观察结果表明，检测不到的TSH浓度比低但可检测的值具有更大的意义。
