Silent thyroiditis after excision of a thymoma

A 61-year-old man developed thyrotoxicosis after excision of a thymoma. His laboratory examination showed an increased level of thyroid hormone and a low thyroidal iodine uptake. No thyroidal autoantibody was detected. With the diagnosis of silent thyroiditis, he was treated with propranolol. He became euthyroid after 2 months. Thymoma often accompanies an autoimmune disease as a paraneoplastic syndrome, and an immunological mechanism is thought to be involved in the onset of silent thyroiditis. This case suggests the involvement of an immunological mechanism in the pathogenesis of silent thyroiditis.