RESUMO
This study determined the relapse rate following the use of antithyroid drugs (ATD) in patients with Graves' disease and assessed T4 suppression test as a follow up index for predicting relapse after carbimazole treatment in 21 patients who had taken 9-12 months of ATD treatment continuously with good compliance. T4 suppression test was done before stopping ATD treatment. During one year of follow up after stopping ATD therapy, 12 (57%) patients relapsed and 9 (43%) remained in remission. Six of the 12 relapses occurred in the first 3 months of stopping ATD therapy. The response following the use of carbimazole therapy was comparable to that reported from iodine sufficient western countries and may be because of the salt iodination programme in our country. T4 suppression test was normal in 14 (66%) and abnormal in 7 (34%) patients. All the patients with abnormal T4 suppression test relapsed after stopping ATD. The overall accuracy of the T4 suppression test (76%) also favourably compared with reported values of other useful but less readily available markers such as thyrotropin releasing hormone (TRH) stimulation test and thyroid receptor antibodies. Thus, in our experience antithyroid drugs were able to induce long term remission in 43 per cent patients with Graves' disease and abnormal T4 suppression test can be used as a reliable parameter for predicting relapse.