The activity of the hypothalamic-pituitary-adrenal axis in hemodialyzed (HD) patients has been investigated, with conflicting results. Different results are reported concerning both basal ACTH and cortisol concentration and the responses to different stimulating agents, in chronic hemodialyzed patients. The present study was performed in order to asses whether the length of the hemodialytic treatment may affect the pituitary and adrenocortical response to stimulation with ovine CRH (oCRH) and with exogenous ACTH in a group of patients on chronic HD for more than 10 years. Ten uremic patients (aged 38-71, 6 males and 4 females) on chronic hemodialysis for at least 10 years and 7 healthy subjects matched for age and sex were studied. The patients were tested on the day preceding dialysis session. Each subject received on different non-consecutive days oCRH (100 micrograms i.v. in bolus) and ACTH (Synacthen 0.25 mg i.v. in bolus), and blood samples were obtained at appropriate intervals. Basal ACTH and cortisol levels of HD patients were in the upper limit of normal range (ACTH 39.21 +/- 11.11 pg/mL in HD patients vs. 26.88 +/- 14.12 pg/mL in controls; cortisol 19.96 +/- 5.07 in HD patients vs. 12.66 +/- 4.44 in controls); however, the means were not significantly different compared with controls. Following oCRH administration a net increase of ACTH and cortisol was observed in every patient tested (ACTH peak 83.81 +/- 28.49 in HD vs. 78.73 +/- 22.87 pg/mL in controls; cortisol peak 30.73 +/- 19.31 in HD vs. 20.05 +/- 3.19 micrograms/dL in controls).(ABSTRACT TRUNCATED AT 250 WORDS)