Low free triiodothyronine predicts poor functional outcome after acute ischemic stroke

• We investigated the association of thyroid hormone and stroke outcome.
• Low FT3 predicted poor functional outcome in patients with ischemic stroke.
• Detrimental effect of FT3 value on outcome increased as FT3 value decreased.
• Neither FT4 nor TSH level were associated with functional outcome.

Background and purposeThe aim of this study was to investigate the association of admission serum thyroid hormone concentration with clinical characteristics and functional outcomes in patients after acute ischemic stroke.MethodsWe retrospectively enrolled 398 consecutive patients admitted to our stroke center between July 2010 and April 2012. Serum thyroid stimulating hormone (TSH), free triiodothyronine (FT3), and free thyroxine (FT4) were evaluated upon admission. Neurological severity was evaluated using the National Institutes of Health Stroke Scale (NIHSS) upon admission and the modified Rankin Scale (mRS) upon discharge. Poor outcome was defined as a mRS score of 3–5 or death (mRS score 6). Separate analyses were conducted according to outcome and quartile serum FT3 concentration.ResultsIn total, 164 patients (41.2%) demonstrated a poor outcome. Age, male gender, blood glucose level, arterial fibrillation, dyslipidemia, smoking, NIHSS score, cardioembolic stroke type, and periventricular hyperintensities, but not FT4 or TSH, were significantly associated with poor functional outcome. Furthermore, poor functional outcome was independently associated with low FT3 (< 2.29 pg/mL). In comparisons between FT3 quartiles (Q1 [≤ 2.11 pg/mL], Q2 [2.12–2.45 pg/mL], Q3 [2.46–2.77 pg/mL], Q4 [≥ 2.78 pg/mL]), patients with poor outcomes were more frequent in Q1 than in Q4 after multivariate adjustment. Death was more frequent in Q1 than in Q4 after adjustment for risk factors and comorbidities, but this difference was non-significant after additional adjustment for age and NIHSS score.ConclusionsOur data suggest that a lower FT3 value upon admission may predict a poor functional outcome in patients with acute ischemic stroke. Further large-scale prospective studies are required to clarify the role of thyroid hormone in the acute phase of ischemic stroke.