Abstract Context The likelihood of remission in patients with autoimmune hyperthyroidism (AH) depends on several prognostic factors. The FT3/FT4 ratio has been suggested as a potential marker of disease severity and prognosis. Objective To evaluate the prognostic value of FT3/FT4 ratio in predicting the likelihood of relapse in patients with AH. Methods This retrospective cohort study included 80 patients with AH diagnosed between 2000 and 2021. Clinical and biochemical data were collected at diagnosis and during follow-up to assess the likelihood of remission in patients attempting to discontinue ATD therapy. ROC analysis and logistic regression were used to identify predictors of relapse. Results Of the 48 patients who discontinued antithyroid therapy, 24 (50%) relapsed, predominantly within 12 months. The FT3/FT4 ratio was significantly higher in patients who relapsed both at diagnosis (median 0.46 vs 0.36; p 0.001) and at ATD withdrawal (median 0.43 vs 0.33; p 0.001). An FT3/FT4 ratio ≥0.42 at diagnosis predicted relapse with 83% sensitivity and 66% specificity. In a multivariate analysis, FT3/FT4 ratio ≥0.42 at diagnosis (OR 7.18; p 0.012) and the presence of orbitopathy were identified as independent predictors of relapse. Longer time to FT3 normalization (p 0.02) and orbitopathy were associated with relapse in univariate analyses (p 0.039). Conclusion The FT3/FT4 ratio, measured both at diagnosis and before antithyroid drug withdrawal, is a significant predictor of relapse in autoimmune hyperthyroidism. This parameter may represent a useful tool for guiding decisions about treatment duration and withdrawal.
Abbate et al. (Mon,) studied this question.