Predictors of outcome and comparison of different drug regimens for the prevention of relapse in patients with Graves' disease

Abstract

Objective: To investigate the effect of different antithyroid drug (ATD) regimens on relapse rates of Graves' disease, and to look for predictors of relapse.

Design and methods: In a prospective two-way factorial randomized clinical trial, 218 patients with Graves' disease were assigned to ATD combined with l-thyroxine (l-T(4)) or ATD alone for 12 Months. After discontinuation of antithyroid therapy, each group was stratified to either 12 Months further treatment with l-T(4) or no treatment. Clinical and biochemical assessments were carried out before treatment, after 3 and 6 weeks, and every third Month for 12 Months. If the patients lacked symptoms of relapse, laboratory tests were performed every third Month for the second Year, and thereafter annually.

Results: The proportion of all patients with relapse was 47.7% 2 Years after withdrawal of ATD. There was no difference in relapse rates between the treatment groups (P=0.217, log--rank test). Smokers had a higher relapse rate than non-smokers (58.4% vs 38.8%, P=0.009). Patients who were thyrotropin-receptor antibody (TRAb) positive after 12 Months of antithyroid therapy had a higher relapse rate than those who were negative (72.5% vs 36.8%, P<0.0001). Similarly, relapse was more frequent (55.5%) in patients having large goiter compared with subjects with small goiter (36.3%, P=0.0007).

Conclusions: Relapse rates of Graves' disease were independent of ATD regimen whether followed by l-T(4) therapy or not. Smoking, large goiter and presence of TRAb at the end of ATD therapy were strong predictors of relapse.