Arginine vasopressin responses to osmotic (0.1 ml.kg-1.min-1 NaCl), orthostatic (standing upright and maintenance of orthostatic position for 20 min), and hypoglycemic (0.15 IU/kg insulin) stimuli were evaluated in women with polycystic ovaries and in normal subjects. Blood dehydroepiandrosterone, dehydroepiandrosterone sulphate, androstenedione, testosterone, cortisol, and endogenous insulin levels were significantly higher in women with polycystic ovaries than in controls, whereas estrone, estradiol-17 beta, progesterone and 17OH-progesterone concentrations were normal in all subjects. Arginine vasopressin basal levels (mean +/- SEM of 3 test days; women with polycystic ovaries: 2.8 +/- 0.2 pmol/l; controls: 2.7 +/- 0.2 pmol/l) and secretory responses to orthostatic (mean peaks 100% higher than baseline values) and to hypertonic (130% increments) stimuli were similar in the two groups. Arginine vasopressin responses to hypoglycemia were lower in women with polycystic ovaries (50% increment) than in controls (150% increment), although comparable blood glucose decrements and GH or cortisol increments were found in the two groups. Arginine vasopressin peak responses to hypoglycemia were negatively correlated to testosterone, androstenedione, and endogenous insulin levels, but did not correlate with basal and hypoglycemia-induced peak cortisol concentrations or with circulating levels of other steroids. These data indicate a hypothalamic posterior pituitary disorder affecting arginine vasopressin response to insulin-induced hypoglycemia in women with polycystic ovaries syndrome associated with elevated blood androgen and insulin concentrations.