Department of Endocrinology, Aalborg Hospital, Aarhus University Hospital, Postbox 365, DK-9100 Aalborg, Denmark.
Nat Rev Endocrinol. 2011 Apr;7(4):232-9. doi: 10.1038/nrendo.2011.13. Epub 2011 Feb 8.
The diagnosis of subclinical hypothyroidism--serum TSH levels above and T(4) levels within the laboratory reference ranges--depends critically on the upper limit of the TSH reference interval. Calls have been made to lower the current upper TSH reference limit of 4.0 mU/l to 2.5 mU/l to exclude patients with occult hypothyroidism. However, data from population studies do not indicate that the distribution of TSH is altered owing to inclusion of such individuals. The opposite suggestion has also been put forward; the TSH upper reference limit is often too low, especially in the elderly, in women and in white individuals, which may lead to unnecessary or even harmful therapy. Studies in elderly individuals have shown that although aging may be associated with increased TSH levels, paradoxically, overt hypothyroidism in this population may be associated with a less robust TSH response than in young individuals. This Review highlights the interindividual and intraindividual variability of TSH levels and discusses the current controversy that surrounds the appropriateness of reference ranges defined on the basis of age, race, sex and amount of iodine intake. Moreover, the current evidence on lowering or increasing the upper limit of the TSH reference interval is reviewed and the need to individualize levothyroxine treatment in patients with elevated TSH levels is discussed.
亚临床甲状腺功能减退症的诊断——血清 TSH 水平高于且 T(4)水平在实验室参考范围内——严重依赖于 TSH 参考区间的上限。人们呼吁将当前的 TSH 参考上限 4.0 mU/l 降低至 2.5 mU/l，以排除隐匿性甲状腺功能减退症患者。然而，来自人群研究的数据并未表明由于纳入此类个体，TSH 的分布发生了改变。相反的观点也被提出；TSH 的上限参考值通常太低，尤其是在老年人、女性和白人中，这可能导致不必要甚至有害的治疗。在老年人中的研究表明，尽管随着年龄的增长，TSH 水平可能会升高，但具有讽刺意味的是，与年轻人相比，该人群中的显性甲状腺功能减退症可能与 TSH 反应不那么强烈有关。这篇综述强调了 TSH 水平的个体内和个体间变异性，并讨论了目前围绕基于年龄、种族、性别和碘摄入量定义参考范围的适当性的争议。此外，还回顾了目前关于降低或提高 TSH 参考区间上限的证据，并讨论了在 TSH 水平升高的患者中个体化左甲状腺素治疗的必要性。
