Brabant G, Beck-Peccoz P, Jarzab B, Laurberg P, Orgiazzi J, Szabolcs I, Weetman A P, Wiersinga W M
Abteilung Gastroenterologie, Hepatologie und Endokrinologie, Medizinische Hochschule, Hannover, Germany.
Eur J Endocrinol. 2006 May;154(5):633-7. doi: 10.1530/eje.1.02136.
Mild forms of hypothyroidism--subclinical hypothyroidism--have recently been discussed as being a risk factor for the development of overt thyroid dysfunction and for a number of clinical disorders. The diagnosis critically depends on the definition of the upper normal limit of serum TSH as, by definition, free thyroxine serum concentrations are normal. Cut-off levels of 4-5 mU TSH/l have been conventionally used to diagnose an elevated TSH serum concentration. Recent data from large population studies have suggested a much lower TSH cut-off with an upper limit of 2-2.5 mU/l but application of strict criteria for inclusion of subjects from the general population studies aiming at assessing TSH reference intervals (no personal or family history of thyroid disease, no thyroid antibodies and a normal thyroid on ultrasonography) did not result in an unequivocal upper limit of normal TSH at 2.0-2.5 mU/l. When summarizing the available evidence for lowered upper TSH cut-off values and their potential therapeutic implications there is presently insufficient justification to lower the upper normal limit of TSH and, for practical purposes, it is still recommended to maintain the TSH reference interval of 0.4-4.0 mU/l. Classifying subjects with a TSH value between 2 and 4 mU/l as abnormal, as well as intervening with thyroxine treatment in such subjects, is probably doing more harm than good.
轻度甲状腺功能减退症——亚临床甲状腺功能减退症——最近被认为是显性甲状腺功能障碍和多种临床疾病发生的危险因素。诊断关键取决于血清促甲状腺激素（TSH）正常上限的定义，因为根据定义，血清游离甲状腺素浓度是正常的。传统上，TSH血清浓度升高的诊断采用4 - 5 mU TSH/L的临界值。来自大型人群研究的最新数据表明，TSH临界值要低得多，上限为2 - 2.5 mU/L，但在旨在评估TSH参考区间的一般人群研究中（无甲状腺疾病个人或家族史、无甲状腺抗体且超声检查甲状腺正常），应用严格的纳入标准并未得出明确的TSH正常上限为2.0 - 2.5 mU/L。在总结关于降低TSH临界值上限及其潜在治疗意义的现有证据时，目前没有足够的理由降低TSH正常上限，出于实际目的，仍建议维持0.4 - 4.0 mU/L的TSH参考区间。将TSH值在2至4 mU/L之间的受试者归类为异常，并对这些受试者进行甲状腺素治疗干预，可能弊大于利。
