Development of Graves' Disease Nine Years After Total Thyroidectomy Due to Follicular Carcinoma of the Thyroid

We report a 49-year-old woman with Marfan syndrome who underwent total thyroidectomy for follicular carcinoma. The patient was given 100 mCi of radioactive iodine (¹³¹I) followed by levothyroxine (LT₄) 0.2 mg/day after surgery. The subsequent five total body scans were negative and thyroglobulin (TG) measurements ranged between undetectable levels to 12 ng/mL. Nine years after thyroidectomy the patient developed bilateral exophthalmos with markedly positive thyroid-stimulating immunoglobulins (TSI), indicating the presence of Graves' disease. TG levels increased and concurrently pulmonary metastases that did not concentrate radioiodine at tracer doses, were diagnosed. Due to these metastatic lesions, the patient received a therapeutic dose of 150 mCi of ¹³¹I 1 month after LT₄ withdrawal, and a total body scan was made 10 days later. Slight uptake of ¹³¹I was found in the right side of the neck, whereas predominant uptake occurred in the right lung base. We suggest that the elevated TSI played a role in the growth of metastases.