Free Triiodothyronine Is Associated with Poor Outcomes after Acute Ischemic Stroke

Abstract

Aims. It is unclear whether thyroid hormones are associated with functional outcomes after ischemic stroke. We aimed to investigate the impact of serum levels of thyroid hormones at admission on functional outcomes at 3 months after acute ischemic stroke. Methods. A total of 480 consecutive patients with ischemic stroke who were admitted to our hospital within 48 h of onset were enrolled. The levels of thyroid hormones, including thyroid-stimulating hormone, free triiodothyronine (FT3), and free thyroxine, were measured at admission, and functional outcomes were assessed at 3 months using the modified Rankin Scale (mRS), with scores ranging from 0 to 6. Poor outcome was defined as mRS score ≥3. Results. FT3 levels at admission were considerably lower in patients with poor outcomes than in those with good outcomes at 3 months (3.53 ± 0.70 pmol/L vs. 4.04 ± 0.68 pmol/L; $P<0.001$ ). Lower FT3 levels were observed in patients with higher mRS scores. Multivariable logistic regression analysis revealed that FT3 levels were significantly associated with a risk of poor outcomes at 3 months, independent of conventional risk factors such as age, National Institutes of Health Stroke Scale score, and recanalized therapy. In addition, patients in FT3 levels in the lowest quartile had a 2.56-fold higher risk of poor outcomes than those with FT3 levels in the highest quartile (odds ratio = 2.56, 95% confidence interval = 1.15–5.69, $P=0.021$ ). The sensitivity and specificity of FT3 level ≤3.69 pmol/L for predicting poor outcomes were 62.70% and 72.03%, respectively. Conclusion. Our study suggests that FT3 levels at admission are significantly and independently associated with a risk of poor outcomes after ischemic stroke and that lower FT3 levels can be considered as a prognostic biomarker for poor outcomes at 3 months.