Langerhans cell histiocytosis (LCH)是一個少見疾病，主要特徵是由Langerhans cells侵入並浸潤在組織中。它的臨床表現變化大，可侵犯任何器官，在內分泌系統中，以中樞性尿崩症表現為最多，侵犯至甲狀腺則極為罕見。我們報告一名原被診斷為中樞性尿崩症以及腦下垂體瘤的15歲男性，發現甲狀腺腫大及甲狀腺功能低下後，經細針穿刺細胞學的檢查，發現許多單核大細胞及嗜伊紅性細胞的浸潤．經甲狀腺部分切除手術後，組織病理檢查證實為LCH。此病人拒絕使用葡萄糖皮質類固醇和化療，因此給予DDAVP和甲狀腺荷爾蒙之補充．中樞性尿崩症是LCH侵犯內分泌器官最常見的症狀，因此應將列入臨床之鑑別診斷，同時也應評估腦下垂體其它荷爾蒙之功能是否正常。

Langerhans cell histiocytosis (LCH) is a rare proliferative disease characterized by Langerhans cells. The clinical presentation is variable, and diabetes insipidus (DI) is common when the disease involves the endocrine system. But thyroid involvement is very rare. We report a 15-year-old male patient with central DI and a pituitary stalk tumor revealed by a brain magnetic resonance imaging (MRI) scan. Primary hypothyroidism developed later, and the thyroid echo showed thyroiditis. Abundant enlarged mononuclear cells and eosinophils were found by fine-needle thyroid aspiration cytology. A partial thyroidectomy was performed, and LCH was confirmed by histopathologic examination. The patient refused glucocorticoids and chemotherapy, desmopressin (DDAVP) and thyroxin were begun. Central DI and pituitary stalk tumor or thickening should be included in the differential diagnosis of LCH, and other hormone deficiencies should be also evaluated.