MON-621 A Second Course of Antithyroid Drug Therapy Is Effective in Patients with Relapsed Graves' Disease

Background: Antithyroid drugs (ATDs) are preferred as a first-line treatment for Graves’ disease (GD). However, around 50-60% of patients relapse following treatment withdrawal. Radioactive iodine (RAI) or thyroidectomy is recommended for these patients, however, repeat ATD therapy is a further option, dependent upon patient choice. The long-term efficacy of ATD in relapsed GD has not been robustly established. Methods: We conducted a retrospective study to assess the prognosis after a second course of ATD and investigate the clinical predictors for remission. Consecutive ATD-treated GD patients with at least three years of follow-up who attended our endocrine service since 2004 were identified and medical records analysed. Remission was defined as maintaining a euthyroid status for at least one year after ATD withdrawal. Results: 219 patients underwent an initial course of ATD therapy. A total of 129 patients (59%) relapsed upon treatment withdrawal after a mean time of 2.0 ± 2.7 years (range 0-15 years). Seventy-two (58%) patients (70% female, age at diagnosis 43.7 ± 15.0 years) opted for a second course of ATD. Eight patients were lost to follow-up. During 6.1 years (range 1.5-11.7 years) median follow-up, 24 patients (38%) achieved remission, 29 patients (45%) relapsed and 17% (n=11) continued ATD treatment. Male gender (RR=1.88, CI 1.21-2.91) and presence of a large goitre (RR=2.07, CI 1.42-3.02) were independent risk factors for relapse. A higher free T4 level at the time of relapse (mean fT4 36.2 ± 20.7 pmol/L vs. 29.6 ± 14.3 pmol/L) was also suggestive of increased risk of relapse following second ATD therapy (p=0.05). Age, smoking status and orbitopathy did not show significant association. Conclusion: A second course of ATD therapy results in a satisfying long-term remission rate (38%) in GD patients. The best outcomes are in females presenting with lower fT4 level on relapse in the absence of a large goitre.