Sampaolo Guido, Campanella Nando, Catozzo Vania, Ferretti Maurizio, Vichi Giovanna, Morosini Pierpaolo
Recenti Prog Med. 2014 Feb;105(2):79-82. doi: 10.1701/1417.15701.
Subclinical hypothyroidism (SH) is settled whenever high levels of serum thyroid-stimulating hormone (TSH) are detected, whereas free thyroid hormone levels are within the normal range. Benefits and risks of therapy for SH have been debated for 2 decades. However, consensus has not yet been achieved. Besides preventing the progression to overt hypothyroidism, the decision of undertaking replacement therapy in SH is made mainly by basing on the risk of metabolic (dyslypidemia) and subsequent cardiovascular complications.
A series, made up of 1756 patients (mean age 42,8±16,8, range 0,5-94) and filed from 1984 to 2013, was studied retrospectively. 169 patients were affected by clinical (overt) hypothyroidism (IC: TSH >40). 1587 patients were affected by SH, out of whom 1121 were mild (TSH <10) and 466 medium (TSH ≥ 10 ≤40). The series of patients was properly followed-up. The mean follow-up time was 6 years. In all patients TSH, Ft4, and total cholesterol were evaluated basally and after appropriate (TSH normalized) medical therapy.
By medical replacement treatment, clinical hypothyroidism (CI) related hypercholesterolemia decreased significantly in 28%. In SH, the baseline serum cholesterol levels were wide. However, replacement treatment did not reduce such levels. No major cardiovascular accident occurred to any patient over the follow-up period.
Hypercholesterolemia is certainly due to CI, therapy reduces cholesterol levels that not always fall below 200 mg/dl and this condition persists over time. SH is not characterized by hypercholesterolemia. Cholesterol levels in these patients are variable equal to the normal people and can not be reduced with thyroxine.
只要检测到血清促甲状腺激素（TSH）水平升高，而游离甲状腺激素水平在正常范围内，即可诊断为亚临床甲状腺功能减退症（SH）。关于SH治疗的益处和风险已经争论了20年。然而，尚未达成共识。除了预防进展为显性甲状腺功能减退症外，SH患者是否进行替代治疗的决定主要基于代谢风险（血脂异常）及随后的心血管并发症。
对1984年至2013年存档的1756例患者（平均年龄42.8±16.8岁，范围0.5 - 94岁）进行回顾性研究。169例患者患有临床（显性）甲状腺功能减退症（IC：TSH>40）。1587例患者患有SH，其中1121例为轻度（TSH<10），466例为中度（TSH≥10≤40）。对该系列患者进行了适当的随访。平均随访时间为6年。对所有患者在基线时以及经过适当（TSH正常化）药物治疗后评估TSH、Ft4和总胆固醇。
通过药物替代治疗，临床甲状腺功能减退症（CI）相关的高胆固醇血症在28%的患者中显著降低。在SH患者中，基线血清胆固醇水平差异较大。然而，替代治疗并未降低这些水平。在随访期间，没有任何患者发生重大心血管事件。
高胆固醇血症肯定是由CI引起的，治疗可降低胆固醇水平，但并不总是降至200mg/dl以下，且这种情况会随着时间持续存在。SH的特征不是高胆固醇血症。这些患者的胆固醇水平与正常人一样存在差异，且不能通过甲状腺素降低。
