Medical School, University of Warwick, Warwick.
Centre for Academic Primary Care, University of Bristol, Bristol.
Br J Gen Pract. 2018 Oct;68(675):e718-e726. doi: 10.3399/bjgp18X698861. Epub 2018 Aug 28.
Thyroid function tests (TFTs) are among the most requested tests internationally. However, testing practice is inconsistent, and potentially suboptimal and overly costly. The natural history of thyroid function remains poorly understood.
To establish the stability of thyroid function over time, and identify predictors of development of overt thyroid dysfunction.
Longitudinal follow-up in 19 general practices in the UK.
A total of 2936 participants from the Birmingham Elderly Thyroid Study (BETS 1) with a baseline TFT result indicating euthyroid or subclinical state were re-tested after approximately 5 years. Change in thyroid-stimulating hormone (TSH), free thyroxine (FT), and thyroid status between baseline and follow-up was determined. Predictors of progression to overt dysfunction were modelled.
Participants contributed 12 919 person-years; 17 cases of overt thyroid dysfunction were identified, 13 having been classified at baseline as euthyroid and four as having subclinical thyroid dysfunction. Individuals with subclinical results at baseline were 10- and 16-fold more likely to develop overt hypothyroidism and hyperthyroidism, respectively, compared with euthyroid individuals. TSH and FT demonstrated significant stability over time, with 61% of participants having a repeat TSH concentration within 0.5 mIU/L of their original result. Predictors of overt hypothyroidism included new treatment with amiodarone (odds ratio [OR] 92.1), a new diagnosis of atrial fibrillation (OR 7.4), or renal disease (OR 4.8).
High stability of thyroid function demonstrated over the 5-year interval period should discourage repeat testing, especially when a euthyroid result is in the recent clinical record. Reduced repeat TFTs in older individuals is possible without conferring risk, and could result in significant cost savings.
甲状腺功能测试（TFTs）是国际上最常要求的测试之一。然而，测试实践不一致，潜在的不理想和过于昂贵。甲状腺功能的自然史仍知之甚少。
确定甲状腺功能随时间的稳定性，并确定显性甲状腺功能障碍发展的预测因素。
英国 19 家普通诊所的纵向随访。
共有 2936 名来自伯明翰老年甲状腺研究（BETS1）的参与者，他们的基线 TFT 结果表明甲状腺功能正常或亚临床状态，大约 5 年后再次接受测试。确定基线和随访之间 TSH、游离甲状腺素（FT）和甲状腺状态的变化。对进展为显性功能障碍的预测因素进行建模。
参与者提供了 12919 人年；发现 17 例显性甲状腺功能障碍，其中 13 例在基线时被归类为甲状腺功能正常，4 例为亚临床甲状腺功能障碍。与甲状腺功能正常的个体相比，基线时亚临床结果的个体发生显性甲状腺功能减退症和甲状腺功能亢进症的风险分别增加了 10 倍和 16 倍。TSH 和 FT 随时间表现出显著的稳定性，61%的参与者重复 TSH 浓度与其原始结果相差 0.5 mIU/L。显性甲状腺功能减退症的预测因素包括胺碘酮（OR 92.1）、心房颤动（OR 7.4）或肾脏疾病（OR 4.8）的新治疗。
在 5 年的间隔期间，甲状腺功能表现出高度的稳定性，这应该阻止重复测试，尤其是当最近的临床记录中显示甲状腺功能正常时。在年龄较大的个体中减少重复 TFT 检查而不增加风险是可能的，并且可以节省大量成本。
