The baseline LH, FSH and testosterone levels and the LH and FSH response to TRH-LHRH administration (delta LH, delta FSH) were investigated in 28 patients meeting the RDC criteria for an acute major depressive disorder, and in 20 healthy persons. Twenty-two patients were also reinvestigated in a state of complete or partial clinical remission. Cross-sectional and longitudinal comparisons were made between the groups divided according to sex and menopausal status. After mathematical correction for age differences, the depressed males with an abnormal DST response showed significantly (P less than 0.03) higher delta FSH in the acute state compared to the controls. No relation could be established between the HPG axis hormone levels and the nocturnal serum melatonin levels or the PRL or TSH response to TRH-LHRH administration. In the longitudinal part of the study, the depressed males with an abnormal DST response showed decreased (P less than 0.03) testosterone levels and increased delta FSH (n.s.) in the acute state compared to remission, in contrast to the males with a normal DST. The present results do not support a hypothesis regarding a stimulus-induced down-regulation of the pituitary LHRH receptors in our patients. The possible mechanisms by which HPA axis activation (as revealed by an abnormal DST response) could influence the HPG axis in depressed patients remain to be elucidated.