Department of Family Medicine, Mayo Clinic, Rochester, Minn.
Department of Family Medicine, Mayo Clinic, Rochester, Minn.
Am J Med. 2014 Mar;127(3):240-5. doi: 10.1016/j.amjmed.2013.11.012. Epub 2013 Dec 11.
In patients treated for hypothyroidism, the usual practice is to monitor thyroid-stimulating hormone values yearly once a therapeutic dosage of levothyroxine is determined. This study investigates whether there are any clinical predictors that could identify a subset of patients who might be monitored safely on a less frequent basis.
With the use of a retrospective study design, 715 patients treated for hypothyroidism who had a normal (ie, therapeutic) thyroid-stimulating hormone value in 2006 while taking levothyroxine were identified. All thyroid-stimulating hormone values were then obtained through December 31, 2012. By using a Cox proportional hazard model, gender, age, body mass index, history of chronic autoimmune thyroiditis, initial thyroid-stimulating hormone level, and levothyroxine dose were analyzed for time to first abnormal thyroid-stimulating hormone value.
Age, gender, history of chronic autoimmune thyroiditis, and body mass index at the time of initial normal thyroid-stimulating hormone were not associated significantly with time to abnormal thyroid-stimulating hormone value. Levothyroxine dose >125 μg/day had an increased hazard ratio of 2.4 (95% confidence interval, 1.7-3.4; P < .0001) for time to first follow-up abnormal thyroid-stimulating hormone value, but dosages less than that did not increase the hazard ratio. One year after the initial normal thyroid-stimulating hormone value, 91.1% of patients taking ≤ 125 μg/day had a continued normal thyroid-stimulating hormone, whereas only 73.3% of patients taking >125 μg/day did. Transformed thyroid-stimulating hormone value (which represents a measure of how far the initial thyroid-stimulating hormone was from the midpoint of the normal range) also had an increased hazard ratio of 1.14 (95% confidence interval, 1.1-1.2; P < .0001) for time to first abnormal thyroid-stimulating hormone value.
For patients receiving ≤ 125 μg/day of levothyroxine, we propose that a testing interval up to 2 years may be acceptable if their thyroid-stimulating hormone is well within the normal range.
在接受甲状腺功能减退症治疗的患者中，通常在确定左甲状腺素的治疗剂量后，每年监测一次甲状腺刺激激素值。本研究旨在探讨是否存在任何临床预测指标，可以确定一组可以更频繁地监测的患者亚组。
采用回顾性研究设计，确定了 715 名接受甲状腺功能减退症治疗且 2006 年服用左甲状腺素时甲状腺刺激激素值正常（即治疗范围内）的患者。然后，在 2012 年 12 月 31 日之前获得了所有甲状腺刺激激素值。使用 Cox 比例风险模型，分析性别、年龄、体重指数、慢性自身免疫性甲状腺炎病史、初始甲状腺刺激激素水平和左甲状腺素剂量与首次异常甲状腺刺激激素值之间的时间关系。
年龄、性别、慢性自身免疫性甲状腺炎病史和初始正常甲状腺刺激激素时的体重指数与异常甲状腺刺激激素值的时间无显著相关性。每天 125μg 以上的左甲状腺素剂量发生首次随访异常甲状腺刺激激素值的风险比增加 2.4（95%置信区间，1.7-3.4；P<.0001），但剂量小于该值并未增加风险比。在初始正常甲状腺刺激激素值后的 1 年内，每天服用≤125μg 的患者中，91.1%的患者甲状腺刺激激素持续正常，而每天服用>125μg 的患者中，只有 73.3%的患者甲状腺刺激激素持续正常。转化后的甲状腺刺激激素值（代表初始甲状腺刺激激素与正常范围中点的距离的度量）也增加了首次异常甲状腺刺激激素值的风险比 1.14（95%置信区间，1.1-1.2；P<.0001）。
对于每天接受≤125μg 左甲状腺素治疗的患者，如果甲状腺刺激激素在正常范围内，我们建议可以接受长达 2 年的检测间隔。
