Antithyroid drug and Graves’ hyperthyroidism. Significance of treatment duration and TRAb determination on lasting remission

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Abstract
Objective: To investigate the significance of treatment with antithyroid drugs longer than 12 months on lasting remission in Graves’ hyperthyroid patients, and to study clinical and laboratory parameters of prognostic value. Patients: Fifty-two untreated Graves’ hyperthyroid patients were assigned at random to two therapeutic groups. They were treated with Carbimazole during 12 and 24 months in Group I (n= 28) and Group II (n= 24), respectively. Measurements: Serum levels of FT4, T3, sTSH and TSH receptor antibody (TRAb) were measured before starting treatment and at regular intervals during treatment and follow-up after drug withdrawal. We compared the relapse rate in both groups of patients, at short (2-yr) and long-term (5-yr) periods after drug withdrawal. Also, we compared clinical and biochemical parameters between patients who stayed in remission and who had relapse. Results: At the end of the short-term period, relapse had occurred in 13 (46.4%) Group I patients and in 13 (54.1%) Group II patients, p=0.36. At the end of the long-term period, relapse had occurred in 24 (85.7%) Group I and 20 (83.3%) Group II patients, p=0.78. No difference could be observed between patients who had stayed in remission and who had suffered relapse, within the 5-yr follow-up period regarding to goiter size, frequency of ophthalmopathy, TSH and TRAb levels. Conclusions: The high relapse rate observed could be due to high iodine intake in our country. In this study and in a review of the available data, we have been unable to find any rational basis for courses of antithyroid drugs longer than twelve months for the treatment of Graves’ hyperthyroidism. Nor is a reliable prognosis for an individual patient possible by TRAb determination at any given time during therapy, owing to the low sensitivity and specificity of this variable.

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