亞臨床甲狀腺疾病

Subclinical Thyroid Disease

白蕙菁(Hui-Ching Pai) ； 龔信宗(Shinn-Tzong Gong)

《內科學誌》 24卷6期 (2013/12) Pp. 469-476

https://doi.org/10.6314/JIMT.2013.24(6).05

摘要

亞臨床甲狀腺疾病（subclinical thyroid disease）通常用來描述輕微的甲狀腺功能亢進或甲狀腺功能低下相關疾病。甲促素（TSH）是實驗室診斷中最重要的檢驗項目，血清中之TSH偏高，但游離四碘甲狀腺素（free T4）及三碘甲狀腺素（T3）正常者，被定義為亞臨床甲狀腺功能低下（subclinical hypothyroidism）；而TSH低於正常值時，Free T4及T3正常者，定義為亞臨床甲狀腺功能亢進（subclinical hyperthyroidism）。一般來說，亞臨床甲狀腺功能低下或甲狀腺功能亢進的盛行率在一般人口中，分別為4%～10%和1%～2%。亞臨床甲狀腺疾病隨年齡增加，發生率增加。雖然亞臨床甲狀腺疾病相當常見，臨床的表現不一，治療與否與年齡、TSH值高低、造成疾病的原因等而有不同的考量，在一般人口中如何篩檢這類亞臨床的疾病目前仍然沒有共識。不過，亞臨床甲狀腺疾病的篩檢，應考慮相關高風險的族群，包括1）老年人；2）有心房顫動病史；3）曾有甲狀腺疾病史者；4）已確認為其他自體免疫性疾病者；5）頸部輻射暴露（例如，鼻咽癌，放射治療後）之病患；6）家族史有疑似為自體免疫性甲狀腺疾病者，以及7）具甲狀腺疾病史的懷孕患者等。而對於治療亞臨床甲狀腺疾病的選擇，需要以病患的狀況，個別考慮。亞臨床甲狀腺功能低下者，給予治療可能減少其進展為明顯之甲狀腺功能低下的風險、改善心臟功能，校正血脂異常，緩解衰老和憂鬱情緒等，可依患者個別情況評估是否給予甲狀腺素補充。亞臨床甲狀腺功能亢進者，其治療策略通常是基於TSH的高低，考量發展成明顯甲狀腺功能亢進的風險、臨床症狀，以及有無併發可能的心臟血管疾病等。治療方法包括抗甲狀腺藥物或放射性碘，至於甲狀腺腫較大者，可以考慮甲狀腺切除治療。

關鍵字

亞臨床甲狀腺疾病（Subclinical thyroid disease） ； 亞臨床甲狀腺功能低下（Subclinical hypothyroidism） ； 亞臨床甲狀腺功能亢進（Subclinical hyperthyroidism）

並列摘要

Subclinical thyroid disease is usually used to describe the symptoms of mild hyperthyroidism or hypothyroidism. Thyrotropin (TSH) is the most important laboratory diagnostic test item. High serum TSH with normal free iodine thyroxine (free T4) and triiodotyronine (T3) is defined as subclinical hypothyroidism. Low serum TSH with normal free T4 and T3 is defined as subclinical hyperthyroidism. The prevalence of subclinical hypothyroidism or hyperthyroidism in the general population is respectively 4~10% and 1~2%. The incidence of subclinical thyroid disease increases with age. Although subclinical thyroid disease is quite common, the clinical symptoms appearance differed in every one; the decision for treatment or not is related to the age, the level of TSH values and the cause of the subclinical thyroid disease. There is still no consensus about how to screen these subclinical diseases in the general population. However, the screening of subclinical thyroid disease should be considered in high-risk patients, including 1) the elderly; 2) with history of atrial fibrillation; 3) with history of thyroid disease; 4) with other autoimmune disease; 5) with history of radiation exposure to neck (e.g. The patient with nasopharyndeal carcinoma received radiation therapy); 6) with family history of autoimmune thyroid disease and 7) pregnant patients with a history of thyroid disease. The choice of treatment for subclinical thyroid disease should be individualized. In subclinical hypothyroidism, Thyroxin supplement may be reduce the risk of progression to overt hypothyroidism, improve cardiac function, correct dyslipidemia, alleviate aging and depression. In subclinical hyperthyroidism, the considerations of treatment are usually based on the level of TSH, the risk of progression to overt hyperthyroidism, the clinical symptoms and the concurrent cardiovascular diseases. The treatment strategies include anti-thyroid drugs or radioactive iodine and thyroid resection can be considered for the larger goiter.