Department of Clinical Studies, Radiation Effects Research Foundation, Hiroshima, Japan.
Thyroid. 2011 Nov;21(11):1177-82. doi: 10.1089/thy.2010.0411. Epub 2011 Aug 30.
Few population-based studies report the changes with time in thyroid function tests in patients with subclinical hypothyroidism. We compared the risk for developing overt hypothyroidism in patients with subclinical hypothyroidism and euthyroid controls from the same population of elderly Japanese. We also sought associations of selected parameters with the development of overt hypothyroidism in the subclinical hypothyroid and euthyroid groups.
We measured thyrotropin (TSH) and free thyroxine (T4) levels at baseline examinations performed from 2000 to 2003 in the cohort of Japanese atomic-bomb survivors and identified 71 patients with spontaneous subclinical hypothyroidism (normal free T4 and TSH >4.5 mIU/L without a history of thyroid treatment, mean age 70 year) and 562 euthyroid controls. We re-examined TSH and free T4 levels an average of 4.2 years later (range, 1.9-6.9).
The risk for progression to overt hypothyroidism was significantly increased in subclinical hypothyroid patients (7.0%) compared with control subjects (1.6%) after adjusting for age and sex (odds ratio, 4.56; p=0.009). Higher baseline TSH levels were associated with progression from subclinical to overt hypothyroidism (p=0.02) in the multivariate analysis, including age, sex, antithyroid peroxidase antibody, and ultrasonography (US) findings. The analysis using binary TSH data suggested that a TSH level >8 mIU/L was a predictive value for development of overt hypothyroidism (p=0.005). On the other hand, serum TSH levels spontaneously normalized in 38 (53.5%) of the patients with subclinical hypothyroidism. In the multivariate analysis, normalization of TSH levels was associated with lower baseline TSH levels (p=0.004) and normal and homogenous thyroid US findings (p=0.04). Atomic-bomb radiation dose was not associated with subclinical hypothyroidism or its course.
Subclinical hypothyroidism was four times more likely to be associated with development of overt hypothyroidism than euthyroid controls in the sample population of Japanese elderly. TSH levels in half of the patients normalized spontaneously when assessed after an average follow-up period of 4.2 years. Baseline TSH level and thyroid US findings are potential predictors of future thyroid function in subclinical hypothyroidism.
很少有基于人群的研究报告亚临床甲状腺功能减退症患者甲状腺功能检测随时间的变化。我们比较了来自同一老年日本人群的亚临床甲状腺功能减退症患者和甲状腺功能正常对照者发生显性甲状腺功能减退症的风险。我们还探讨了亚临床甲状腺功能减退症和甲状腺功能正常组中选定参数与显性甲状腺功能减退症发展的关系。
我们在 2000 年至 2003 年期间对日本原子弹幸存者队列进行了基线检查，测量了促甲状腺激素（TSH）和游离甲状腺素（T4）水平，确定了 71 例自发性亚临床甲状腺功能减退症患者（正常游离 T4 和 TSH>4.5mIU/L，无甲状腺治疗史，平均年龄 70 岁）和 562 例甲状腺功能正常对照者。平均 4.2 年后（范围 1.9-6.9）再次检查 TSH 和游离 T4 水平。
亚临床甲状腺功能减退症患者进展为显性甲状腺功能减退症的风险明显高于对照组（7.0%比 1.6%），调整年龄和性别后（比值比 4.56；p=0.009）。多变量分析包括年龄、性别、抗甲状腺过氧化物酶抗体和超声（US）发现，较高的基线 TSH 水平与从亚临床到显性甲状腺功能减退症的进展相关（p=0.02）。使用二项 TSH 数据的分析表明，TSH 水平>8mIU/L 是发展为显性甲状腺功能减退症的预测值（p=0.005）。另一方面，38 例（53.5%）亚临床甲状腺功能减退症患者的血清 TSH 水平自发正常化。多变量分析显示，TSH 水平正常化与较低的基线 TSH 水平（p=0.004）和正常且均匀的甲状腺 US 发现相关（p=0.04）。原子弹辐射剂量与亚临床甲状腺功能减退症或其病程无关。
在日本老年人群样本中，亚临床甲状腺功能减退症患者发生显性甲状腺功能减退症的可能性是甲状腺功能正常对照者的四倍。在平均随访 4.2 年后评估时，一半患者的 TSH 水平自发正常化。基线 TSH 水平和甲状腺 US 表现是亚临床甲状腺功能减退症未来甲状腺功能的潜在预测因素。
