Risk Factors for the Relapse of Graves' Disease Following Withdrawal of Antithyroid Drugs

Objectives: The treatment of Graves' disease (GD) with antithyroid drugs (ATD) is associated with a risk of relapse. The rate and predictive factors of GD are controversial. This study aimed to assess the relapse rate after the withdrawal of ATD in patients with GD, as well as to identify its predic-tive factors. Material and Methods: This was a retrospec-tive cohort study covering 35 patients with GD that were treated with ATD. Relapse was defined as the state when hyperthyroidism was detected after the withdrawal of me-dical therapy. Relapse was studied by establishing the sur-vival curve according to Kaplan-Meier's method. The Log-Rank test was used to compare the survival curves ac-cording to the clinical, biological, and therapeutic parame-ters of the patients. Results: The mean follow-up time after the withdrawal of ATD was 32.8128.8 months. Relapse was observed in 13 patients (37%) after an average time of 7.818.8 months of ATD discontinuation. Factors associated with the risk of relapse were smoking (p=0.08), family his-tory of thyroid disease (p=0.03), the presence of a trigge-ring factor (p=0.004), FT4 level at the time of diagnosis at >2.3 times the normal range (p=0.002), thyroid -stimula-ting hormone level less than 0.76 mIU/L at three months after ATD withdrawal (p=0.05), and a benzylthiouracil dose of >125 mg/day at the time of ATD discontinuation (p=0.02). Conclusion: Relapse in patients with GD after the withdrawal of ATD is observed in almost a third of the patients. Identification of patients at a high risk of relapse is necessary to indicate radical treatment.