EFFECT OF METHIMAZOLE, WITH OR WITHOUT L-THYROXINE, ON REMISSION RATES IN GRAVES-DISEASE

Medical treatment of Graves' disease involves antithyroid drugs with o r without the addition of exogenous T-4. There have been conflicting r eports as to whether the addition of T-4 improves remission rates or d elays relapse. To evaluate this issue in a North American population, 199 patients were treated with methimazole until they were euthyroid. They were then randomized to either methimazole alone in a dose suffic ient to normalize TSH (group 1), or to 30 mg methimazole daily plus su fficient T-4 to maintain TSH in the upper normal range (group 2), or t o 30 mg methimazole daily plus sufficient T-4 to suppress TSH below 0. 6 mIU/L (group 3). After 18 months, methimazole was stopped, and T-4 w as continued in groups 2 and 3. Because not all patients in groups 2 a nd 3 achieved their target TSH concentration, they were reassigned to group A (TSH greater than or equal to 1.0) or group B (TSH < 1.0), bas ed on the mean TSH achieved during methimazole treatment. One hundred forty-nine patients have been followed for at least 6 months after sto pping methimazole (mean 27 months). Fifty-eight percent of patients ha ve relapsed. There were no significant differences in relapse rates af ter stopping methimazole. Among those patients who did relapse, howeve r, there was a significant difference in the months to relapse after s topping methimazole between groups B and 1 (group 1: 3.3 +/- 0.7, grou p A: 5.6 +/- 0.8, group B: 7.4 +/- 1.7; P = 0.01 for the comparison be tween groups B and 1). We conclude that the addition of T-4 to methima zole does not improve long-term remission rates in Graves' disease.