A prospective randomized study was performed in patients with hyperthyroid Graves’ disease (GD) in order to compare long (18 months) and short term (6 months) antithyroid drug treatment on the remission rate. A therapeutic protocol was offered to all GD patients who had not been treated for this disease previously. All patients studied who followed the protocol were rechecked 2 yr after treatment was withdrawn, or earlier in the case of relapse. Of the patients having undergone long term treatment, 61.8% still were in remission 2 yr after treatment withdrawal, whereas only 41.7% of the patients treated for 6 months were in remission (P < 0.05). Such findings clearly establish that treatment duration has a direct beneficial incidence on the remission rate. These results were confirmed by the fact that treatment for 18 months resulted in remission in 7 of 15 patients who had previously relapsed after a 6-month course of therapy. This improvement in relation to treatment duration might be due to the immunosuppressive action of carbimazole. No significant difference was observed between relapse and remission groups, regardless of treatment duration, for HLA ABDr, serum T3 and T4, and T3/T4 ratio determined before treatment. Only the thyroid-stimulating antibody levels determined at the time of diagnosis and at the end of treatment were higher in the relapse group, a difference that was relevant only globally, due to value scattering. Furthermore, thyroidstimulating antibody levels at the end of treatment may indicate remission or, conversely, continuance of the pathological process. These results demonstrate that prolonged (18 months) rather than short term (6 months) antithyroid drug treatment significantly improves the remission rate in GD. © 1990 by The Endocrine Society.
