甲狀腺激素抗性症（Resistance to thyroid hormone, RTH）是一種罕見的遺傳性疾病，主要由於甲狀腺素受體基因突變，導致組織對甲狀腺素反應降低。此疾病特徵為血清中游離三碘甲狀腺素（free T3）及甲狀腺素（free T4）濃度升高，但甲狀腺刺激素（TSH）濃度正常或輕度升高。臨床上，患者可能同時表現出甲狀腺素過多與不足的症狀，例如心跳過快、甲狀腺腫大、身材矮小與注意力不足等。由於本病與其他甲狀腺疾病在臨床表現與實驗室數值上有所重疊，診斷上具有挑戰性，因此進行鑑別診斷對於後續治療至關重要。本報告描述一名64歲男性，因過去甲狀腺機能亢進接受甲狀腺切除手術，術後持續接受左旋甲狀腺素（levothyroxine）治療，但血中TSH濃度持續偏高，且free T3與free T4亦異常升高。影像學並未發現腦下垂體異常，且整體臨床表現高度懷疑甲狀腺激素抗性症。本病例提醒臨床醫師，對於出現非典型甲狀腺功能異常的患者，應納入甲狀腺激素抗性症的考量，以提高診斷準確性並制定適當的治療策略。

Resistance to thyroid hormone is a rare genetic disorder characterized by re-duced tissue responsiveness to thyroid hormones due to mutations in thyroid hor-mone receptor genes. This condition leads to elevated serum free triiodothyronine and thyroxine levels with normal or mildly elevated thyroid-stimulating hormone levels. Clinically, patients may exhibit symptoms of both thyroid hormone excess and deficiency, including tachycardia, goiter, short stature, and attention deficit dis-orders. Diagnosis can be challenging due to the overlap with other thyroid disorders, making differential diagnosis essential for appropriate management. Here we present a case of a 64-year-old man with a history of thyroidectomy for hyperthyroidism, who demonstrated persistent elevation of thyroid-stimulating hormone alongside high triiodothyronine and thyroxine levels despite ongoing levo-thyroxine therapy. The absence of pituitary abnormalities and the clinical profile led to the suspicion of resistance to thyroid hormone. This case highlights the im-portance of considering resistance to thyroid hormone in patients with atypical thy-roid function tests and emphasizes the need for heightened awareness to ensure ac-curate diagnosis and effective treatment strategies.