Objective To investigate the correlation between subclinical hypothyroidism (SCH) and cerebral atherosclerosis burden in patients with large artery atherosclerotic stroke.Methods Consecutive inpatients with acute large artery atherosclerotic stroke were enrolled.SCH was defined as TSH 4.50-10.0 mU/L and serum thyroxine level was normal.Cerebral atherosclerosis burden score was used to evaluate the severity of cerebral atherosclerosis.The total score of 1 or 2 was defined as mild atherosclerosis,and >2 was defined as severe atherosclerosis.Univariate analysis and multivariate logistic regression analysis was used to evaluate the correlation between SCH and severe cerebral atherosclerosis.ResultsA total of 263 patients with large artery atherosclerotic stroke were enrolled,including SCH 62 (23.6%),mild atherosclerosis 119 (45.2%),and severe atherosclerosis 144 (54.8%).The age (63.6±10.9 years vs.60.5±11.4 years;t=2.274,P=0.024),homocysteine (17.10±6.20 μmol/L vs.15.63±5.17 μmol/L;t=2.058,P=0.041),National Institutes of Health Stroke Scale (NIHSS) score (8.0 [5.0-10.0]vs.6.0 [5.0-9.0];Z=2.059,P=0.039),as well as the proportions of patients with hypertension (72.9%vs.58.8%;χ2=5.812,P=0.016),smoking (38.2%vs.26.1%;χ2=4.366,P=0.037),and SCH (30.6%vs.15.1%;χ2=8.610,P=0.003) in the severe cerebral atherosclerosis group were significantly higher than those in the mild cerebral atherosclerosis group.Multivariate logistic regression analysis indicated that SCH was an independent risk factor for severe atherosclerosis in patients with large atherosclerotic stroke (odd ratio 3.345;95%confidence interval 1.692-6.612;P=0.001) after adjusting for age,sex,hypertension,smoking,homocysteine,and NIHSS score.ConclusionSCH is an independent risk factor for severe cerebral atherosclerosis in patients with large atherosclerotic stroke.