Thyroid-Stimulating Immunoglobulin Levels During Low-Dose Antithyroid Therapy Predict Graves' Disease Relapse

Phong Vu Nhat NguyenKhue Thy Nguyen^*

• University of Medicine and Pharmacy at Ho Chi Minh City, Ho Chi Minh City, Vietnam

Background: Graves' disease (GD) is a common autoimmune disorder often treated with antithyroid drugs (ATD), but relapse rates remain high after therapy withdrawal. This study evaluates the role of thyroid-stimulating immunoglobulin (TSI) levels in predicting relapse after ATD discontinuation in GD patients. Methods: A retrospective analysis of 349 GD patients who achieved euthyroid status on maintenance ATD therapy was conducted. TSI levels were measured using a chemiluminescent immunoassay. Of these, 88 patients discontinued ATD therapy and were monitored for relapse. Statistical analyses, including receiver operating characteristic curve analysis, were used to identify relapse predictors. Results: The median TSI level was significantly higher in patients who relapsed (1.63 vs. 0.52 IU/L, p<0.01), and a cutoff of 1.31 IU/L yielded 63.64% sensitivity, 78.79% specificity, and 86.67% negative predictive value. Independent relapse predictors included a TSI ≥1.31 IU/L, treatment duration of less than 18 months, and the presence of thyroid eye disease. Conclusion: TSI measurement is a valuable tool for predicting relapse after ATD withdrawal in GD. A TSI cutoff of 1.31 IU/L can aid in clinical decision-making, but further prospective studies are required to confirm these findings.