Background:Endothelial dysfunction probably has a role in the etiology of sudden sensorineural hearing loss (SSNHL). The aim of this study was determining of the relationship between endothelial dysfunction and SSNHL.Materials and Methods:In a case–control study, 30 patients with SSNHL and 30 otherwise healthy age and sex-matched controls were studied. Demographic data gathered included age, gender, family history of SSNHL, and history of smoking, cardiovascular disease, hypertension, diabetes, and dyslipidemia. Laboratory data included measurement of hemoglobin, fasting blood sugar (FBS) and lipid profile. Endothelial function was assessed by measuring flow-mediated dilation (FMD).Results:The two groups were the same in age (47.9 ± 9.3 and 48.1 ± 9.6 years, P = 0.946) with female/male ratio of 1:1 in both groups. Diabetes and dyslipidemia were more frequent in patients than controls (20% vs. 0%, P = 0.024). Brachial artery diameter was greater in patients than controls before (4.24 ± 0.39 vs. 3.84 ± 0.23 mm, P < 0.001) and after ischemia (4.51 ± 0.43 vs. 4.28 ± 0.27 mm, P = 0.020), but FMD was lower in patients than controls (6.21 ± 3.0 vs. 11.52 ± 2.30%, P < 0.001). Binary logistic regression analysis showed that FMD was associated with SSNHL independent from FBS and lipid profile (odds ratio [95% confidence interval] =0.439 [0.260–0.740], P = 0.002).Conclusion:Endothelial dysfunction, among other cardiovascular risk factors, is associated with SSNHL. This association is independent from other cardiovascular risk factors including diabetes and dyslipidemia.