Methimazole (MMI) has been used in subjects with Graves' disease. Although in clinical medicine its starting dose was dependent on the judgment of each physician in charge, the Japan Thyroid Association treatment guidelines recommended that we should start MMI at a dose of 15mg/day especially in subjects with mild Graves' disease with a baseline free T4 (FT4) levels between 0.24pmol/L (1.9ng/dL) and 0.64pmol/L (5ng/dL) from the viewpoint of preventing side effects [1,2]. Based on such background, in this study we examined which background factors influence on the effect of 15mg/day of methimazole in Japanese subjects with mild Graves' disease.
