Abstract Body: Introduction
Subclinical hyperthyroidism has been linked to an increased risk of atrial fibrillation, which elevates the likelihood of cardioembolism, cryptogenic stroke (CS), and embolic stroke of undetermined source (ESUS). However, the broader relationship between thyroid function abnormalities and acute ischemic stroke remains uncertain. This study aims to investigate whether patients with acute ischemic stroke due to cardioembolism, CS, or ESUS are more likely to have abnormal thyroid-stimulating hormone (TSH) levels compared to those with ischemic strokes from other etiologies, as classified by the TOAST criteria.

Methods
Utilizing data from the Get With The Guidelines Database, we conducted a retrospective chart review of patients admitted to our single comprehensive stroke center, diagnosed with an acute ischemic stroke between August 2022 and January 2023. The Kruskal-Wallis rank sum test was employed to assess differences in TSH, Free T4, and, if available, one year follow-up TSH levels among patients with ischemic stroke etiologies of small vessel disease, large artery atherosclerosis, cardioembolism, CS, and ESUS.

Results
A total of 211 patients were included in the analysis, the distribution of stroke etiologies included 33 (16%) with small vessel disease, 51 (24%) with large artery atherosclerosis, 77 (36%) with cardioembolism, 13 (6.2%) with an undetermined/cryptogenic etiology, and 25 (12%) with ESUS. The majority of patients had normal TSH levels, accounting for 82% of the total cohort, the overall mean TSH level was 2.52 (reference range 0.27-4.2uIU/mL). No significant differences were observed in the mean TSH (p = 0.066), Free T4 (p = 0.13), or follow-up TSH (p = 0.79) levels across each stroke subtype.

Conclusions
Our findings suggest that thyroid function does not significantly differ across the various etiologies of acute ischemic stroke, as classified by TOAST criteria. While further large-scale studies are warranted, our results indicate that routine evaluation of thyroid function may not be essential in the determination of stroke etiology.