IS THERE A METHIMAZOLE DOSE-EFFECT ON REMISSION RATE IN GRAVES-DISEASE - RESULTS FROM A LONG-TERM PROSPECTIVE-STUDY

OBJECTIVE The optimal antithyroid drug regimen for Graves' disease rem ains a matter of controversy. The European Multicentre Trial Group has investigated the effects of methimazole drug dose on the long-term ou tcome of Graves' disease. DESIGN Extended follow-up of patients from a prospective multicentre trial, designed to study methimazole dose eff ects on the outcome of Graves' disease. We have reported previously th at the relapse rates did not differ after a medication-free observatio n period of 12 months; the relapse rates were 37 and 38%, respectively . In this paper, we describe the outcome in these patients after a mea n observation period of 4.3 +/- 1.3 years and have looked for potentia l predictors of this outcome. PATIENTS Three hundred and thirteen pati ents with Graves' disease were randomized to treatment with a constant dose of 10 or 40 mg of methimazole for 1 year, with levothyroxine sup plementation as required. MEASUREMENTS At the time of inclusion into t he trial: thyroid size, T4, T3, TSH-binding inhibiting immunoglobulins , urinary iodide excretion, thyroid uptake, Crook's therapeutic index of hyperthyroidism (a measure of clinical disease severity). At the ti me of follow-up examination: TSH, T4, T3, thyroid size, thyroid ultras ound, THS-binding inhibiting immunoglobulins. RESULTS The overall rela pse rate was 58%. There was no difference in relapse rates between pat ients treated with either 10 or 40 mg of methimazole (58.3 vs. 57.8%). Five patients had become spontaneously hypothyroid, without obvious r elationship to antithyroid drug dose. Patients who relapsed and patien ts who remained in remission did not differ with respect to: age, goit re size, ophthalmopathy, median iodine excretion, serum T4 or serum T3 , Crook's therapeutic index and thyroid uptake at the time of study en try. Thus, none of these variables was potentially suitable for predic ting outcome. This finding was confirmed by Cox's proportional hazard regression. Thyroid volume, measured by ultrasound, did not differ bet ween patients in remission and patients with relapse. There was no dif ference in the course of endocrine eye signs, in the requirement for s teroid and radiotherapy for eye signs, or in thyroid echo-structure be tween patients in the 10 and in the 40 mg group, nor was serum TSH dif ferent in patients who had remained in remission (0.8 +/- 0.6 mU/l in the 10 mg group, 1.0 +/- 0.8 mU/l in the 40 mg group). CONCLUSIONS The dose of methimazole in Graves' disease therapy can safely be kept to the minimal required dose. This will provide the same chance of remiss ion as higher doses, and provide the best balance of risk and benefit.