Severe hyperthyroidism due to metastatic papillary thyroid carcinoma with favorable outcome.

A case of extremely severe hyperthyroidism due to bone metastasis of papillary thyroid cancer is described. Hyperthyroidism began in this patient soon after the discovery of pelvic metastasis and worsened after total thyroidectomy and after the first dose of radioiodine. The administration of methimazole, prednisone and multiple, fractioned and small doses of radioiodine cured the hyperthyroidism and stabilized the neoplastic growth. Hyperthyroidism lasted for at least six months and hypothyroidism appeared only after seven months. Thus, the fractionation of the doses of radioiodine together with antithyroid drugs appears to be an effective treatment in patients with hyperthyroidism due to metastatic thyroid cancer.