BACKGROUND:Recently, subclinical hypothyroidism has been associated with increased carotid intima-media thickness, but it is controversial. OBJECTIVE:To assess whether carotid intima-media thickness in patients with subclinical hypothyroidism differs from that in euthyroid subjects. METHODS:We searched published studies concerning the carotid intima-media thickness of patients with subclinical hypothyroidism in comparison with euthyroid subjects. Then, we evaluated each potential study for eligibility, assessed the methodological quality, and extracted the data for a Meta-analysis. RESULTS:Eight observational studies with 3 602 cases met the eligibility criteria. In patients with subclinical hypothyroidism, the pooled estimate of the weighted mean difference (WMD) of increased carotid intima-media thickness was 0.056 [95%CI (0.020, 0.092)]. Sensitivity analysis using a pooled result of the seven higher-quality studies demonstrated higher carotid intima-media thickness level in patients with subclinical hypothyroidism than in euthyroid subjects [WMD=0.064, 95%CI(0.024, 0.105)]. In a subgroup analysis, subclinical hypothyroidism was even more significantly associated with the carotid intima-media thickness in patients with a mean thyrotropin level > 10.0 mU/L [WMD=0.082, 95%CI (0.049, 0.116)]. Subclinical hypothyroidism was also associated with a significant increase in systolic blood pressure, triglyceride levels, total cholesterol levels, low-density lipoprotein levels and with a decrease in fasting plasma glucose. This meta-analysis indicates that subclinical hypothyroidism is associated with an increased carotid carotid intima-media thickness, which may be due to elevated thyrotropin, dyslipidemia and hypertension. Despite the obvious individual differences, a prospective large-sample study is necessary to further assess the conclusions of this observation.