The aim of this study was to evaluate the presence of early vascular damage in young normal-weight women with polycystic ovary syndrome (PCOS). Thirty young normal-weight women with PCOS, who had no additional metabolic or cardiovascular diseases, and 30 healthy women (controls) matched for age and body mass index were studied. A complete hormonal assay was performed in each subject. Serum insulin and glucose levels were measured at baseline and after the oral glucose tolerance test. Plasma endothelin-1 levels and serum lipid profile were also assessed. The endothelial function was studied by flow-mediated dilation on the brachial artery, and arterial structure was evaluated by intima-media thickness measurement using Doppler ultrasound of both common carotid arteries.A significant (P < 0.05) difference in flow-mediated dilation (14.3 +/- 1.9% vs. 18.1 +/- 2.0% for PCOS patients and controls, respectively) and in intima-media thickness (0.53 +/- 0.09 mm vs. 0.39 +/- 0.08 mm for PCOS patients and controls, respectively) was found between PCOS and control subjects. Serum endothelin-1 levels were also significantly (P < 0.05) higher in PCOS patients compared with controls (1.1 +/- 0.4 pmol/liter vs. 0.5 +/- 0.2 pmol/liter for PCOS patients and controls, respectively).In conclusion, our data show that young, normal-weight, nondyslipidemic, nonhypertensive women with PCOS have an early impairment of endothelial structure and function.