Objective:In the current study, we aimed to investigate whether thyroid autoimmunity (TA) had any effect on carotid intima-media thickness (cIMT) and enhanced the risk of cardiovascular disease (CVD) independent of thyroid function (TF) in pubertal girls with Hashimoto’s thyroiditis (HT).Methods:Sixty-six newly diagnosed euthyroid girls with HT with a mean age of 14.4±2.4 years were included in the study. The control group consisted of 41 age- and body mass index (BMI)-matched healthy girls. At enrollment, all subjects underwent physical examination including blood pressure, standing height, weight, waist circumference (WC), and hip circumference measurements. The lipid profile, high-sensitivity C-reactive protein (hs-CRP), homocysteine, blood glucose, insulin, TF, and thyroid antibodies were measured, and thyroid ultrasound and cIMT were performed.Results:There were no significant differences in anthropometric variables between the two groups, but the patients with HT had significantly higher waist-to-hip ratio (WHR). Thyroid hormones, insulin, homocysteine, and homeostatic model assessment-insulin resistance were not different between the two groups. Serum hs-CRP levels were significantly higher in patients than controls (3.4 ng/mL vs. 2.03 ng/mL), (p<0.001). Patients were also characterized by significantly higher total cholesterol (166.4±27 mg/dL vs. 151±22 mg/dL), (p<0.01) and low-density cholesterol (95.8±24.4 mg/dL vs. 82.6±20.7 mg/dL), (p<0.01) levels. Patients, regardless of TF, had significantly increased cIMT compared with controls [0.28 mm vs. 0.25 mm, (p<0.001)], and cIMT was correlated with weight-standard deviation score (SDS), BMI-SDS, WC-SDS, and WHR. This increase in cIMT was associated independently with BMI-SDS and hs-CRP levels.Conclusion:TA may be related to chronic inflammation, which may cause endothelial dysfunction, a promoter of atherosclerosis in girls with HT. cIMT is a good tool for the early detection and the monitoring of early atherosclerosis in euthyroid patients with HT. Early detection of risk factors of CVD, may be helpful for planning treatment and interventions, so as to prevent complications from the disease in adulthood.