亚临床甲状腺功能减退症

亚临床甲状腺功能减退症（甲减）是一种亚临床甲状腺疾病。诊断标准是血清促甲状腺激素（TSH）水平高于正常上限而游离T4水平尚在正常范围。目前全世界亚临床甲减的平均患病率为4％-10％，主要发生在女性和老年人群。桥本甲状腺炎是最常见的病因。其主要的临床危害包括引起血脂异常、导致动脉粥样硬化和冠心病、影响认知功能，还可导致不孕和流产。治疗主要针对血清TSH〉10ml U／L的患者，应用左旋-T4替代治疗。对于血清TSH4～10ml U／L，特别是甲状腺自身抗体阳性者需密切监测。此外，对妊娠期亚临床甲减患者的治疗要求控制TSH〈2．5ml U／L。

Subclinical hypothyroidism

Subclinical hypothyroidism is one of subclinical thyroid diseases, which is defined as ＂a serum thyroid stimulating hormone（TSH） concentration above the statistically defined upper limit of the reference range when serum free T4 concentration is within its reference range＂. The average worldwide prevalence has been reported to be in the range of 4% -10% , mainly among women and the elderly. The most commonly cause of subclinical hypothyroidism is Hashimoto＇s thyroiditis. Subclinical hypothyroidism is associated with disorders of serum lipid, development of atherosclerosis and cardiovascular disease, presence of cognitive impairment, infertility and miscarriage. L-thyroxine substitutive therapy is recommended when TSH is above 10 ml U/L. Patients with serum TSH between 4 and 10 mlU/L should be monitored frequently especially if thyroperoxidase antibody is positive. The goal of the therapy for the pregnant women with subclinical hypothyroidism is serum TSH less than 2.5 ml U/L.