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The Free T3/Free T4 Ratio Predicts Relapse After Antithyroid Drug Withdrawal in Pediatric Autoimmune Hyperthyroidism
Marco Abbate1, Gaia Vincenzi1, Stefano Mora2
1Department of Pediatrics, Endocrine Unit, IRCCS San Raffaele Scientific Institute, Milan 20132, Italy.
The Journal of Clinical Endocrinology and Metabolism
|March 31, 2026
Summary
The FT3/FT4 ratio can predict relapse in autoimmune hyperthyroidism (AH). A higher ratio at diagnosis or before stopping treatment indicates a greater risk of relapse, aiding treatment decisions.
Area of Science:
- Endocrinology
- Internal Medicine
- Clinical Chemistry
Background:
- Autoimmune hyperthyroidism (AH) remission likelihood depends on prognostic factors.
- The FT3/FT4 ratio is a potential marker for AH disease severity and prognosis.
Purpose of the Study:
- To evaluate the prognostic value of the FT3/FT4 ratio in predicting relapse likelihood in AH patients.
Main Methods:
- Retrospective cohort study of 80 AH patients (2000-2021).
- Collected clinical and biochemical data at diagnosis and follow-up.
- Used ROC analysis and logistic regression to identify relapse predictors.
Main Results:
- 50% of patients (24/48) who discontinued antithyroid drugs (ATD) relapsed, mostly within 12 months.
- Higher FT3/FT4 ratio at diagnosis (0.46 vs 0.36) and ATD withdrawal (0.43 vs 0.33) in relapsed patients.
- FT3/FT4 ratio ≥0.42 at diagnosis predicted relapse (83% sensitivity, 66% specificity) and was an independent predictor (OR 7.18).
Conclusions:
- FT3/FT4 ratio at diagnosis and before ATD withdrawal predicts AH relapse.
- This ratio can guide treatment duration and withdrawal decisions.
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