Background

Thyroid hormone plays a pivotal role in human metabolism. In epidemiologic studies, adequate registration of thyroid disorders is warranted. We examined the prevalence of thyroid disorders, reported thyroid medication use, thyroid hormone levels, and validity of thyroid data obtained from questionnaires in the Lifelines Cohort Study.

Methods

We evaluated baseline data of all 152180 subjects (aged 18–93 years) of the Lifelines Cohort Study. At baseline, participants were asked about previous thyroid surgery and current and previous thyroid hormone use. At follow-up (n = 136776, after median 43 months), incident thyroid disorders could be reported in an open, non-structured question. Data on baseline thyroid hormone measurements (TSH, FT4 and FT3) were available in a subset of 39935 participants.

Results

Of the 152180 participants, mean (±SD) age was 44.6±13.1 years and 58.5% were female. Thyroid medication was used by 4790 participants (3.1%); the majority (98.2%) used levothyroxine, and 88% were females. 59.3% of levothyroxine users had normal TSH levels. The prevalence of abnormal TSH levels in those not using thyroid medication was 10.8%; 9.4% had a mildly elevated (4.01–10.0 mIU/L), 0.7% had suppressed (<0.40 mIU/L), while 0.7% had elevated (>10.0 mIU/L) TSH levels. Over 98% of subjects with TSH between 4 and 10 mIU/L had normal FT4. Open text questions allowing to report previous thyroid surgery and incident thyroid disorders proved not to be reliable and severely underestimated the true incidence and prevalence of thyroid disorders.

Conclusions

Undetected thyroid disorders were prevalent in the general population, whereas the prevalence of thyroid medication use was 3.1%. Less than 60% of individuals using levothyroxine had a normal TSH level. The large group of individuals with subclinical hypothyroidism (9.4%) offers an excellent possibility to prospectively follow the natural course of this disorder. Both structured questions as well as linking to G.P.’s and pharmacists’ data are necessary to improve the completeness and reliability of Lifelines’ data on thyroid disorders.

中文翻译：

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生命线队列研究中的甲状腺疾病流行病学（荷兰）

背景

甲状腺激素在人体新陈代谢中起关键作用。在流行病学研究中，必须对甲状腺疾病进行充分的登记。我们检查了甲状腺疾病的患病率，报告的甲状腺药物使用情况，甲状腺激素水平以及从生命线队列研究调查表中获得的甲状腺数据的有效性。

方法

我们评估了生命线队列研究的所有152180名受试者（18-93岁）的基线数据。在基线时，询问参与者以前的甲状腺手术以及当前和以前的甲状腺激素使用情况。在随访中（中位43个月后，n = 136776），可以通过一个开放的，非结构性的问题报告甲状腺疾病。在39935名参与者的子集中可获得基线甲状腺激素测量值（TSH，FT4和FT3）的数据。

结果

在152180名参与者中，平均（±SD）年龄为44.6±13.1岁，女性为58.5％。4790名参与者（3.1％）使用了甲状腺药物；大部分（98.2％）使用左甲状腺素，女性为88％。59.3％的左甲状腺素使用者的TSH水平正常。未使用甲状腺药物者中TSH水平异常的发生率为10.8％；9.4％轻度升高（4.01–10.0 mIU / L），0.7％抑制（<0.40 mIU / L），而0.7％的TSH水平升高（> 10.0 mIU / L）。TSH在4至10 mIU / L之间的受试者中，有超过98％的FT4正常。允许报告先前的甲状腺手术和甲状腺疾病事件的开放文本问题被证明是不可靠的，并且严重低估了甲状腺疾病的真实发病率和患病率。

结论

未检测到的甲状腺疾病在普通人群中普遍存在，而使用甲状腺药物的患病率为3.1％。不到60％的使用左甲状腺素的患者的TSH水平正常。大量亚临床甲状腺功能减退症患者（9.4％）提供了极好的可能性来预期性地遵循这种疾病的自然过程。结构化问题以及与GP和药剂师数据的链接对于提高Lifelines甲状腺疾病数据的完整性和可靠性都是必要的。