Obesity and insulin resistance but not hyperandrogenism mediates vascular dysfunction in women with polycystic ovary syndrome

Objective: Polycystic ovary syndrome (PCOS) is associated with biochemical evidence of early atherosclerosis; however, data regarding vascular function are controversial. We hypothesized that resistance vessel function (mediated by the endothelium or smooth muscle) would be impaired in women with PCOS and aimed to determine the contribution of hyperandrogenism, obesity, or insulin resistance to vascular dysfunction. Design: Prospective study. Setting: University practice. Patient(s): Women with PCOS (n = 24) and age/weight-matched controls (n = 22). Intervention(s): Vascular function was assessed by measuring forearm vasodilation in response to both endothelium-dependent (acetylcholine/bradykinin) and endothelium-independent dilators (nitroprusside/verapamil). Main Outcome Measure(s): Resistance vessel function. Result(s): Forearm vasodilation to all four drugs was reduced (> 50%) in obese PCOS compared to lean PCOS subjects. There was no significant difference in vascular function between obese or lean women with PCOS compared to corresponding controls. Androgen levels did not correlate with vascular function. Stepwise regression analysis showed that body mass index (BMI) contributed maximally to vascular dysfunction (R-2 = 0.47). Conclusion(s): This comprehensive study demonstrates for the first time that obese women with PCOS have markedly reduced vascular smooth muscle function compared to lean subjects with PCOS. In our study obesity and insulin resistance, but not hyperandrogenism, appeared to be significant modulators of vascular function.