Objective: Although antithyroid drugs (ATD) are widely used in the treatment of Graves' disease, management protocols, especially treatment duration, remain a subject of debate. The rate of relapse after short-term regimens of less than 6 months with ATD at decreasing doses is higher than after longer treatments from 12 to 24 months. As no prospective study has provided data on even longer protocols exceeding 2 years, we conducted a prospective trial to determine potential benefits of a 42-month treatment compared with an 18-month treatment.
Design, patients and measurements: The aim of this prospective randomized trial was to compare relapse rates achieved two years after treatment withdrawal in patients who received carbimazole at decreasing doses for 18 months (n = 62) vs 42 months (n = 72). In addition to clinical relapse rate, the percentage of patients who normalized antithyroperoxidase (TPO) antibody and anti-TSH receptor stimulating antibody (TSAb) levels and early iodine uptake at the end of treatment were assessed as outcome criteria.
Results: The relapse rate two years after discontinuation of treatment did not differ significantly in patients treated for 18 months from those treated for 42 months (36% vs 29%, NS). At the end of treatment, there was no significant difference between the two groups in the percentage of anti-TPO positive patients (53% vs 46%, NS) or early iodine uptake (27% vs 21%, NS). Although the percentage of patients with TSAb was significantly lower in the 42-month treatment group (18% vs 42%, P = 0.004) at treatment withdrawal, the percentage of TSAb-positive patients did not significantly decrease between 18 and 42 months in this group (27% vs 18%, NS).
Conclusion: Treatment duration greater than 18 months did not improve remission rate determined 2 years after treatment withdrawal or immunological variables or early iodine uptake measured at the time of discontinuation of treatment. These findings would indicate that, when a defined duration treatment is planned, prolonging treatment beyond 18 months does not provide any additional benefit.