OBJECTIVE: Hirsutism is frequently present in patients with polycystic ovary syndrome (PCOS) and is a major sign of hyperandrogenism. However, other disorders frequently present in PCOS, particularly abdominal obesity and insulin resistance (IR), have also been implicated in the development of hirsutism in this population but relevant data are limited. We aimed to define the determinants of the presence of hirsutism in PCOS.DESIGN: Observational study.METHODS: We studied 1297 patients with PCOS (age 24.3±5.8 years, BMI 26.8±6.9 kg/m(2)). Hirsutism was defined as a modified Ferriman-Gallwey score ≥8.RESULTS: Women with hirsutism were younger, had greater BMI, and had higher levels of circulating androgens than women without hirsutism; markers of IR did not differ between the two groups after adjustment for age and BMI. The prevalence of hirsutism progressively declined with age, was lower in normal-weight women than in overweight and obese women, and was comparably prevalent in the hyperandrogenemic phenotypes of PCOS. In binary logistic regression analysis, independent predictors of the presence of hirsutism were younger age, larger waist circumference (W), and higher serum testosterone levels. In stepwise linear regression analysis, the Ferriman-Gallwey score independently correlated with age, W, free androgen index, and serum Δ4-androstenedione and DHEAS levels.CONCLUSIONS: Besides hyperandrogenemia, abdominal obesity, and young age are independently associated with the presence of hirsutism. In contrast, the relationship between IR and hirsutism appears to be mediated by the more severe obesity of insulin-resistant patients with PCOS.