As all PCOS women were anovulatory, they underwent a progesterone challenge test (100 mg natural progesterone i.m.; Prontogest, Amsa, Rome, Italy), which induced uterine bleeding in all PCOS women. To exclude the presence of type 2 diabetes or abnormal glucose tolerance, the oral glucose tolerance test (OGTT) was performed and the normal glucose response to the OGTT was defined according to the 'Report of the Expert Committee on the diagnosis and classification of diabetes mellitus'.