Clinical significance of low T3 syndrome in different subtypes of cerebral infarction

Objective To explore the mechanism underlying the poor prognosis in cerebral infarction (CI) patients with low T3 syndrome by comparing the NIHSS scores in these patients with or without low T3 syndrome.Methods One hundred and sixty-two patients with CI,admitted to our hospital from January 2010 to December 2012,were chosen in our study; the levels of thyroid hormones,including triiodothyronine (T3),four iodine thyronine (T4),thyroid stimulating hormone (TSH),free Triiodothyronine (iT3) and free four iodine thyronine (fT4),were measured by radioimmunoassay.CI lesions and TOAST distribution were determined by cranial MRI,magnetic resonance angiography (MRA) or CT angiography (CTA),and carotid ultrasonography.NIHSS scores at the worst in cerebral infarction inpatients were detected.Results In the 162 patients with CI,29 patients (17.90％) were combined with low T3 symptom and 20 had fT3 level lower than the lowest normal level (2.63 pmol/L); and T4,fT4 and TSH levels were within normal limits.T3,fr3 and TSH levels in patients with low T3 symptom were significantly lower than those of patients without low T3 symptom (P＜0.05).The distribution of TOAST showed no significant difference between patients with low T3 symptom and patients without low T3 symptom (P＞0.05).In patients with large artery atherosclerosis-internal carotid artery,the NIHSS scores at the worst in patients with low T3 level were significantly higher as compared with those in patients with normal T3 levels (P＜0.05).Conclusion The neurologic impairment is more severe in large artery atherosclerosis-intemal carotid artery patients with low T3 level than those without low T3 level,which might be responsible for the poor prognosis of the illness with low T3 syndrome. Key words: Cerebral infarction;  Low T3 syndrome;  Neurological deficit