BACKGROUND: In addition to the negative effect on fertility, polycystic ovary syndrome (PCOS) has been associated with cardiac pathology. Brain natriuretic peptide (BNP) is a possible marker for cardiac risk, therefore we investigated whether N-terminal pro-B-type BNP (NT-proBNP) increases in women with PCOS compared with healthy women of comparable age and body mass index. METHODS: Thirty women with PCOS and 30 healthy women not suffering from overt cardiac disease were involved in the study. Fasting insulin and serum NT-proBNP levels were measured, and M-Mode echocardiography was performed. Insulin resistance was calculated using the homeostasis model assessment insulin resistance index (BOMA-IR). RESULTS: PCOS subjects had higher NT-proBNP levels than the control subjects (P < 0.001). Abnormal echocardiography indices were detected in 14 of the PCOS subjects (but none of the controls), including valvular heart disease in nine, diastolic dysfunction in two, right ventricular enlargement in one, right atrial enlargement in one and pulmonary hypertension in one. PCOS subjects (n = 30) showed an increased left ventricular mass (LVM) (P < 0.001) and left ventricular posterior wall thickness (LVPWT) (P = 0.006). In addition, NT-proBNP concentration was positively correlated with LVM (r = 0.587, P = 0.001) and negatively correlated with sex-hormone-binding globulin (r = -0.528, P = 0.003). There was a positive correlation between LVM and HOMA-IR (r = 0.295, P = 0.03) while LVPWT was positively correlated with fasting insulin and HOMA-IR (r = 0.335, P = 0.031 and r = 0.346, P = 0.045, respectively) in PCOS subjects (n = 30). CONCLUSION: The present study demonstrated that the level of NT-proBNP was increased in PCOS subjects with asymptomatic heart disease.