It has been suggested that neuroendocrine regulation plays an important role in the pathogenesis and activation of autoimmune diseases. The aim of this investigation was to clarify the hypothalamic-pituitary response to a well-defined stimulus under standardised conditions in patients with SLE. Plasma concentrations of prolactin (PRL), growth hormone (GH) and cortisol were determined in venous blood drawn through an indwelling cannula during insulin-induced hypoglycaemia (0.1 U/kg b.w., i.v.) in ten patients and in 12 age-, gender- and weight-matched healthy subjects. Basal PRL concentrations were higher in patients vs healthy controls (12 vs 6 ng/ml, P < 0.01), though still within the physiological range. Insulin-induced plasma PRL and GH were significantly increased both in patients and healthy subjects; however, the increments or areas under the curves were not different in the two groups. Plasma cortisol response showed moderate attenuation in patients. Sensitivity of pituitary lactotrothrops to thyrotropin-releasing hormone (TRH) administration (200 microg, i.v.) was the same in patients and control subjects. In SLE patients with low activity of the disease the sensitivity of pituitary PRL release to TRH administration remained unchanged. The hypothalamic response to stress stimulus (hypoglycaemia) was comparable in patients and healthy subjects.