Treatment of hyperthyroidism with radioiodine: adjunctive therapy with antithyroid drugs reconsidered.

To assess the value of antithyroid drugs as an adjunct to radioactive iodine for the treatment of hyperthyroidism the incidence of relapse or hypothyroidism after a mean follow-up of 5 1/2 years (range 2-7 years) was reviewed retrospectively for 206 patients, some treated with and others without antithyroid drugs after radioiodine therapy. Allocation to treatment group had been random, and both groups were similar in all respects except for the adjunctive treatment with antithyroid drugs. All doses of 131I had been calculated by one physician. Compared with those who received 131I alone, those starting on antithyroid drugs within 8 days after 131I had a lower incidence of hypothyroidism but a higher incidence of early post-treatment recurrence or persistence of hyperthyroidism, and a considerably lower incidence of remission.