Hürthle cell carcinoma of the thyroid presenting as thyrotoxicosis

Objective: To report a case of hyperthyroidism associated with Hürthle cell carcinoma and to review the literature regarding this relationship. Methods: We describe the clinical, biochemical, radiologic, and pathologic data of a patient with Hürthle cellcarcinoma associated with thyrotoxicosis and reversible heart failure. We discuss the mechanistic aspects and review previously reported cases of functionalHürthle cellcarcinomas.Results: A 43-year-old womanpresented with thyrotoxicosis and nonischemic cardiomyopathy. She had a "hot" nodule inthe left lobe of the thyroid onsodium pertechnetate scan. She underwent a left hemithyroidectomy and isthmusectomy. Pathologic findings revealed a minimally invasive Hürthle cellcarcinoma. Onfollow-up, the dilated cardiomyopathy had resolved. The associationof thyroid carcinoma with thyrotoxicosis is rare.Conclusions: Some Hürthle cellcarcinomas canbe functionaland lead to thyrotoxicosis. To our knowledge, we present the first case of reversible dilated cardiomyopathy due to thyrotoxicosis originating from Hürthle cell carcinoma.