Endocrine Abstracts

Introduction: Although thyrotoxicosis is considered to be a very rare finding in a patient with thyroid cancer, there are several reports regarding this unexpected association in specialty literature. A frequent cause of thyrotoxicosis in patients with cardiac disease is amiodarone-induced thyroid dysfunction. The mechanism underlying this adverse reaction can be attributed to high iodine content and the direct toxic effect of the drug on thyroid cells.

Case report: We present the case of a male patient, age 69, treated with amiodarone for paroxistic atrial fibrillation, which addressed our service for a large anterior cervical mass which was observed by the patient two months before presentation. Initial laboratory evaluation revealed thyrotoxicosis and the neck ultrasound revealed a very large anterior cervical hypoechoic mass which appeared of thyroid origin and which extended to the submandibular region and retrosternal. The contrast CT scan of the neck, thorax and abdomen revealed large non-homogenous thyroid mass extended cervical and thoraco-mediastinal with sternal invasion and bilateral pulmonary nodules. The fine needle aspiration and the immunohistochemistry results where consistent with undifferentiated thyroid carcinoma. The I131 scintigraphy of the thyroid revealed non-homogeneous distribution of I131 with areas with no captation in both thyroid lobes. The patient underwent external radiation therapy and chemotherapy. Since 09.2017, he was started on sorafenib and now is on substitutive treatment with levothyroxine.

Conclusions: There are few cases reported in specialty literature of undifferentiated thyroid cancer in patient with amiodarone therapy, but the question whether this rare finding is influenced by high iodine content in the antiarrhythmic drug is still unanswered.