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The Association Between FT4/FT3 Ratio and Prognosis in Ischemic Stroke: A Retrospective Cohort Study
1Neurological Rehabilitation Center, Beijing Rehabilitation Hospital, Capital Medical University, Beijing, China.
Background And Aim:
The FT4/FT3 ratio reflects thyroid hormone metabolism and has emerged as a prognostic marker in cardiovascular diseases. However, its role in ischemic stroke (IS) remains unclear. This study aimed to investigate the association between the FT4/FT3 ratio and 3-month functional outcomes in IS patients.
Methods:
We conducted a retrospective cohort study of 199 first-episode IS patients admitted within 14 days of onset between June 2021 and June 2023. Serum thyroid stimulating hormone (TSH), free triiodothyronine (FT3), and free thyroxine (FT4) were evaluated upon admission. Neurological severity was assessed using the National Institutes of Health Stroke Scale (NIHSS) at admission. Functional outcomes were evaluated using the modified Rankin Scale (mRS) at 3 months post-stroke. Poor outcome was defined as an mRS score of 3-5. Separate analyses were conducted according to FT4/FT3 ratio and outcome.
Results:
Patients were stratified by median FT4/FT3 ratio (3.75) into low (≤ 3.75, n = 100) and high (> 3.75, n = 99) ratio groups. The high-ratio group had lower FT3 (4.14 ± 0.52 vs. 4.68 ± 0.52 pg/mL, p < 0.001), higher FT4 (17.83 ± 2.10 vs. 15.36 ± 1.69 pmol/L, p < 0.001), more diabetes (52.5% vs. 34%, p = 0.010), and higher proportion of poor outcomes (46.5% vs. 28%, p = 0.007). Receiver operating characteristic (ROC) analysis revealed that the FT4/FT3 ratio demonstrated the highest predictive ability (area under the curve [AUC] = 0.662) with an optimal cut-off of 3.845. After adjusting for NIHSS scores, age, sex, and vascular risks, the FT4/FT3 ratio remained an independent predictor of poor outcomes (odds ratio [OR] = 2.589, 95% confidence interval [CI]: 1.171 - 5.727, p = 0.019). FT4 was a risk factor (OR = 1.324, 95% CI: 1.045 - 1.678, p = 0.020), while FT3 showed a nonsignificant protective trend (OR = 0.551, 95% CI: 0.218 - 1.390, p = 0.207).
Conclusion:
An elevated FT4/FT3 ratio may serve as a novel biomarker for predicting poor outcomes in ischemic stroke, reflecting thyroid hormone metabolic dysfunction that potentially exacerbates inflammation and impairs neuronal repair.
Limitations:
This study is limited by its small sample size, single-center design, and absence of serial hormone measurements.
