SummaryDESIGNThere are conflicting data on hypothalamic‐pituitary‐adrenal (HPA) axis function in women with polycystic ovary syndrome (PCOS). We have evaluated the HPA axis responses to naloxone in patients with PCOS compared to control subjects.PATIENTSTwenty PCOS patients and 10 control women participated in the study.MEASUREMENTSOn days 5–6 Of a spontaneous or progestin induced cycle each patient received an intravenous bolus (5 mg) of naloxone (time 0 min), followed by a 2‐mg naloxone infusion In 100 ml of 0.9% saline over one hour. Samples were collected at −30, 0, 15, 30, 60, 90 and 120 minutes. ACTH and cortisol levels were measured in all plasma samples.RESULTSPCOS patients showed significantly greater response than controls to naloxone of ACTH (peak value 261vs172% of basal value) and cortisol (peak value 237 vs 165% of basal value); also, ACTH and cortisol incremental areas were higher In PCOS patients (P<0.05 andP<0.04 respectively).The cortisol/ACTH ratio of AUCs percentage increase was found to be near unity for all patients without significant difference between PCOS and control groups, suggesting a direct correspondence between ACTH circulating levels and adrenal cortisol production.CONCLUSIONSPolycystic ovary syndrome patients showed a hypothalamic‐pituitary‐adrenal axis hyper‐responsiveness to naloxone infusion compared with control subjects. These data support the hypothesis that this disturbance could be ce