['To investigate the adrenal response in terms of allopregnanolone secretion in a group of hyperinsulinemic patients with polycystic ovary syndrome (PCOS).', 'Controlled clinical study.', 'Patients with PCOS in a clinical research environment.', 'Twenty-two overweight patients with PCOS with hyperinsulinism were enrolled after informed consent.', 'All patients underwent hormonal evaluations, oral glucose tolerance test (OGTT) and adrenocorticotropic hormone (ACTH) test before and after 4 months of metformin administration (500 mg p.o. bi-daily). Ultrasound examinations and Ferriman-Gallway score were also performed. Main outcome measures. plasma luteinizing hormone (LH), follicle stimulating hormone (FSH), prolactin (PRL), estradiol, 17-hydroxy-progesterone (17OHP), androstenedione (A), testosterone (T), allopregnanolone, glucose, insulin, C peptide concentrations, body mass index (BMI).', 'Metformin administration reduced significantly LH, A, T, insulin and BMI, while allopregnanolone was significantly increased with no change in progesterone plasma levels. Insulin response to OGTT decreased and allopregnanolone response to ACTH stimulation before while this was restored after the treatment interval. The Ferriman-Gallway score as well as the ovarian volume was significantly decreased after 4 months of metformin therapy.'] Does metformin administration restore allopregnanolone response to adrenocorticotropic hormone ( ACTH ) stimulation in overweight hyperinsulinemic patients with PCOS?