125I Therapy in Graves' Disease

Because of the physical and radiobiologic differences between 125I and 131I, a trial using 125I to treat hyperthyroidism was undertaken in the hope of controlling hyperthyroidism without causing subsequent hypothyroidism. Three hundred fifty-five patients with diffuse toxic goitres were treated and have been under review for an average of 49.4 months: 63.4% are euthyroid, 33.5% are hypothyroid, and 3.1% remain hyperthyroid. Different groups of patients received a wide range of doses of 125I (4.0 to 56.0 mCi), and the lowest incidence of hypothyroidism (23%) was in the group that received between 6.0 and 10.5 mCi. Sixty-three percent of the patients whose initial dose was greater than 20.0 mCi are hypothyroid. Persistent hyperthyroidism was common in patients who received small doses. Because of the high incidence of posttreatment hypothyroidism in this series and because 131I has stood the test of time, we believe that 131I is the radionuclide of choice for the routine treatment of hyperthyroidism.