Remission and relapse rates in Graves' disease treated with methimazole: a 20-year retrospective cohort study.

OBJECTIVE: To evaluate remission and relapse rates in patients with Graves' disease treated with methimazole and to identify clinical and laboratory predictors of these outcomes. SUBJECTS AND METHODS: We conducted a retrospective cohort study of 425 adult patients newly diagnosed with Graves' disease at a single tertiary center between 2002 and 2022. All patients received methimazole for at least 12 months. Remission was defined as drug-free biochemical euthyroidism for 12 months or longer after therapy withdrawal. Univariate and multivariate logistic regression models were used to identify clinical and laboratory predictors of remission and relapse. RESULTS: The mean age was 42.1 ± 13.6 years, and 84.5% were female. The mean duration of methimazole therapy was 36.2 ± 27.9 months. Remission was achieved in 149 patients (35.1%). Of these, 48 (32.2%) experienced relapse, with a median time to relapse of 7 months. Baseline TRAb negativity was the only independent predictor of remission (odds ratio: 2.02; 95% confidence interval: 1.03-3.94; p = 0.039). The degree of TRAb elevation, age, sex, smoking, and thyroid eye disease were not significantly associated with remission. No robust independent predictors of relapse were identified, although a trend was observed in younger patients. Adverse events were rare (1.6%). CONCLUSION: Long-term methimazole therapy in Graves' disease resulted in a modest remission rate of 35.1%, with approximately one-third of these patients experiencing early relapse following drug withdrawal.