Betatrophin is a newly identified hormone determined to be a potent inducer of pancreatic beta cell proliferation in response to insulin resistance in mice. Polycystic ovary syndrome (PCOS) is an inflammatory-based metabolic disease associated with insulin resistance. However, no evidence is available indicating whether betatrophin is involved in women with PCOS. The objective of this study was to ascertain whether betatrophin levels are altered in women with PCOS. This study was conducted in secondary referral center. This cross-sectional study included 164 women with PCOS and 164 age- and BMI-matched female controls. Circulating betatrophin levels were measured using ELISA. Metabolic and hormonal parameters were also determined. Circulating betatrophin levels were significantly elevated in women with PCOS compared with controls (367.09 +/- 55.78 vs. 295.65 +/- 48.97 pg/ml, P < 0.001). Betatrophin levels were positively correlated with insulin resistance marker homeostasis model assessment of insulin resistance (HOMA-IR), free-testosterone, high-sensitivity C-reactive protein (hs-CRP), atherogenic lipid profiles, and BMI in PCOS. Multivariate logistic regression analyses revealed that the odds ratio for PCOS was 2.51 for patients in the highest quartile of betatrophin compared with those in the lowest quartile (95 % CI 1.31-4.81, P = 0.006). Multivariate regression analyses showed that HOMA-IR, hs-CRP, and free-testosterone were independent factors influencing serum betatrophin levels. Betatrophin levels were increased in women with PCOS and were associated with insulin resistance, hs-CRP, and free-testosterone in these patients. Elevated betatrophin levels were found to increase the odds of having PCOS. Further research is needed to elucidate the physiologic and pathologic significance of our findings.