Anaplastic carcinoma of the thyroid in a patient receiving radio-iodine therapy for amiodarone-induced thyrotoxicosis

We describe a case of amiodarone-induced thyrotoxicosis following heart valve replacement in a patient with a multinodular goitre. He responded to medical therapy with carbimazole and potassium perchlorate. Subsequent therapy with radio-iodine was followed 30 weeks later by the development of anaplastic thyroid carcinoma. It is possible that amiodarone caused a low uptake of radio-iodine by the thyroid. It is not known whether this possible low dose exposure to ionising radiation played a part in the development of the anaplastic carcinoma.