University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.
Int J Clin Pract. 2020 Jul;74(7):e13499. doi: 10.1111/ijcp.13499. Epub 2020 May 3.
Subclinical hypothyroidism (SCH) is an asymptomatic condition associated with increased thyroid-stimulating hormone (TSH) >4 mIU/L with normal thyroxine (T4) and triidothyronine (T3) levels. It is more common in older subjects and especially in women with an overall incidence of 10%.
Because the normal TSH levels increase with age up to 7.5 mIU/L in older people, several studies have reported either no benefits whereas others have reported the benefits of treatment. These studies have caused a great debate over the treatment of SCH, especially in older subjects. Therefore, the objective of this study was to review the current evidence over this debate by reviewing the recent literature on the subject to discern whether treatment of SCH is necessary and under what circumstances.
To get a better perspective on the current debate over treatment of SCH, a focused Medline search of the English language literature was conducted from 2012 to 2019 using the terms, hypothyroidism, subclinical, dyslipidaemia, cardiovascular disease, heart failure and 38 papers with pertinent information were selected.
The analysis of results from these papers indicated that the normal levels of TSH are increasing with the advancement of age from 4 mIU/L up to 7.5 mIU/L for patients ≥75 years of age. Also, several of reviewed studies have shown no benefits of treatment whereas, others have shown definite benefits of treatment with levothyroxine supplementation on the clinical and metabolic effects of SBH with reductions in CVD, HF and mortality. The treatment is more effective in younger persons and less so in older persons.
Based on the overall evidence, treatment of SCH is indicated in younger persons with a TSH level >4.0 mIU/L. In older subjects, treatment should be individualised and based on the presence of symptoms, the level of TSH, and initiated at TSH levels ≥10 mIU/L and at low doses to avoid adverse cardiovascular effects from overtreatment.
亚临床甲状腺功能减退症（SCH）是一种无症状的疾病，其特征是促甲状腺激素（TSH）>4 mIU/L 而甲状腺素（T4）和三碘甲状腺原氨酸（T3）水平正常。这种情况在老年人中更为常见，尤其是女性，总发病率为 10%。
由于正常 TSH 水平会随着年龄的增长而升高，在老年人中可达 7.5 mIU/L，因此一些研究报告称治疗没有益处，而另一些研究则报告了治疗的益处。这些研究在 SCH 的治疗方面引起了很大的争议，尤其是在老年人中。因此，本研究的目的是通过回顾该主题的最新文献来审查目前关于该争议的证据，以确定 SCH 的治疗是否有必要，以及在何种情况下有必要。
为了更好地了解目前关于 SCH 治疗的争议，我们对 2012 年至 2019 年期间的英语文献进行了有针对性的 Medline 搜索，使用的术语包括甲状腺功能减退症、亚临床、血脂异常、心血管疾病、心力衰竭，并选择了 38 篇具有相关信息的论文。
对这些论文结果的分析表明，随着年龄的增长，正常的 TSH 水平从 4 mIU/L 升高至 7.5 mIU/L，年龄≥75 岁的患者中更为常见。此外，一些已审查的研究表明治疗没有益处，而其他研究则表明左甲状腺素补充治疗 SBH 的临床和代谢效应具有明确的益处，可降低 CVD、HF 和死亡率。这种治疗在年轻人中更有效，在老年人中效果较差。
根据总体证据，TSH 水平>4.0 mIU/L 的年轻人需要进行 SCH 治疗。在老年人中，治疗应个体化，根据症状、TSH 水平，并在 TSH 水平≥10 mIU/L 时开始低剂量治疗，以避免过度治疗引起的不良心血管影响。
