慢性自體免疫甲狀腺炎或橋本氏甲狀腺炎是造成幼兒及兒童甲狀腺功能低下的主要因素，然而少見於四歲以下的兒童。臨床上，慢性自體免疫甲狀腺炎及先天性甲狀腺功能低下，對幼兒的生長及發育，皆會產生相同之後遺症，因此，早期正確的診斷，對於後遺症的預防，在臨床上是非常重要議題。我們報告一四歲男童，雖然新生兒篩撿正常，但常常食慾不佳，且生長遲緩等主訴，到本院門診就診，為鑑別甲狀腺相關疾病因素，安排甲狀腺功能放射免疫血清檢查、過搭酸甲狀腺閃爍造影及超音波影像診斷，發現患者甲狀腺功能明顯低下，甲狀腺閃爍造影及超音波皆呈現典型慢性自體免疫甲狀腺炎表現，此外，血清中抗甲狀腺抗體及過氧化?抗體價數非常高，最後，經細針針吸細胞學診斷為橋本氏甲狀腺炎。本文針對此二種非侵入性影像診斷，在小兒慢性自體免疫甲狀腺灸診斷之價值做一討論。

Chronic autoimmune thyroiditis is the major cause of hypothyroidism for young children; however, it is rare before the age of four years. In clinic, the same sequela will be developed due to hypothyroidism resulting from both of chronic autoimmune thyroiditis and congenital hypothyroidism. Early and accurate diagnosis of autoimmune thyroiditis becomes very important to pre-vent the tragedy for young children. In this article, we present a four-year-old boy who was diagnosed as hypothyroidism due to poor appetite and short stature. Typical thyroid scintigraphic and ultrasonographic findings of autoimmune thyroiditis were identified in the patient. Significant elevation of serum antibodies of anti-thyroglobulin and anti-peroxidase were demonstrated later. Hashimoto's thyroiditis was diagnosed by fine needle aspiration cytology, finally. We discussed the value of image diagnosis for autoimmune thyroiditis.