Comparison of RA 131I treatment protocols for Graves' disease.

The efficacy of 131I therapy in achieving euthyroidism has been studied in a group of 264 patients followed for up to 10 yr. One hundred and eighty-six were given a dose adjusted for thyroid size and radioactive iodine uptake (Protocol 1), and a second group received the same dosage followed by antithyroid drug therapy plus potassium iodide for 15 days (Protocol 2). At 10-yr follow-up, 50-60% of patients were euthyroid. 25-29% of patients required 2 doses of 131I, and 4-5% required 3 doses. Fewer patients became hypothyroid when their pretreatment FTI was above the average value. More patients became hypothyroid, if their pretreatment test for antimicrosomal antibodies was positive. Patients who required a second dose of radioactive iodide had a significantly greater chance of having worsening of their ophthalmopathy than those who became hypothyroid after the first dose. Treatment with radioactive iodide under either protocol appears to achieve euthyroidism at 10 yr with an incidence higher than that achieved by antithyroid drugs and comparable to that reported for subtotal thyroidectomy.