To evaluate the long-term efficacy of
sodium ipodate (IPO) in the treatment of
hyperthyroid Graves' disease, we studied 12 consecutive patients with Graves'
hyperthyroidism treated only with 500 mg IPO po daily for several weeks to 22 months. Serum
thyroid hormone concentrations markedly decreased and serum free T3 values normalized in all patients within 7 days of
therapy. Five patients (42%, Group 1) were euthyroid after 6 weeks of IPO treatment and remained so until IPO was discontinued after 22 months. Recurrence of
hyperthyroidism after
drug withdrawal occurred in only one of these Group 1 patients, who was promptly responsive to a second course of IPO. In contrast, seven of 12 patients (58%, Group 2) relapsed with recurrent
hyperthyroidism between 14 and 42 days of IPO
therapy. After IPO was withdrawn, these Group 2 patients were treated with
methimazole (20-30 mg/day, initial dose), but the therapeutic response was poor and delayed. Two patients were still
hyperthyroid after 6 months of
methimazole treatment. Elevated serum FT3 concentrations were observed in the Group 2 patients at 21 days following the early normalization of serum FT3 concentrations. No changes in serum
thyroglobulin and thyroid microsomal and
TSH-receptor autoantibody titers were observed in either groups during IPO
therapy. In conclusion, the results of the present study demonstrate that IPO rapidly restores euthyroidism, but its prolonged administration is associated with a high rate of relapse of
hyperthyroidism and a poor response to subsequent
methimazole treatment and that long-term IPO administration does not affect humoral markers of thyroid autoimmunity.