Tosi F, Villani M, Migazzi M, et al. - In the present study, the researchers sought to assess insulin action on glucose and lipid oxidation, non-oxidative glucose metabolism, and serum free fatty acid in different PCOS phenotypes. One hundred and eighty-seven non-diabetic women were diagnosed with PCOS using the Rotterdam criteria. As reference values, data from a historical sample of 20 healthy women were used. Insulin-mediated substrate utilization is impaired in women with PCOS, regardless of their phenotypes. This phenomenon is more prevalent in individuals who have the classic phenotype. Free testosterone affects insulin action abnormalities in glucose and lipid metabolism in an independent way.