Remission of Graves' hyperthyroidism treated with methimazole.

Long-term thionamide treatment is considered one of the main resources for Graves' hyperthyroidism. Although a 54.2% remission rate in patients so treated in Mexico was previously reported, most articles have shown a wide variation over time. In the present article we report the actual remission rate of long-term methimazole (MMZ) therapy of Graves' hyperthyroidism in Mexico. We carried out a retrospective study of long-term MMZ treatment in 80 patients with Graves' hyperthyroidism with a postreatment follow-up of at least twelve months. Remission was considered by clinical as well as biochemical criteria. We studied 63 females and 17 males, mean age 37.7 +/- 10.4 years. Duration of symptoms was 13.3 +/- 20.7 months. Daily MMZ dose: 20.0 +/- 8.8 mg, treatment duration 16.7 +/- 8.9 months and follow-up was 34.8 +/- 60.3 months. Fourteen patients (17.5%) are in remission and sixty six relapsed (82.5%). Relapse occurred after a mean of an 11.9 +/- 11.8 month follow-up. Goiter size was the only statistically significant remission sign whereas age, disease duration, MMZ dose, exophthalmos, treatment duration or 1-thyroxine concomitant use were not useful predictive factors. Remission rate of long-term MMZ treatment of Graves' hyperthyroidism has substantially decreased in Mexico, since the previous report. We suggest that our results may be related to an increase of iodine intake or poor treatment, compliance. Goiter size was the only remission predictive sign. Due to our low remission rate we suggest Graves' disease patients must be selected for this kind of treatment.