Diurnal cortisol responses to dextroamphetamine in normal subjects.

(1) Dextroamphetamine, in doses of 0.1 and 0.15 mg/kg, was administered intravenously morning and evening to normal young men and postmenopausal women, and plasma cortisol responses were assessed. (2) There were no differences in cortisol responses between the young men and older women at either dose. (3) The higher dose elicited a significant and reliable acute cortisol release, while the lower dose did not. (4) In the evening, 0.15 mg/kg amphetamine elicited a larger cortisol increase from baseline than the same dose in the morning. (5) Within morning or evening periods, baseline cortisol values were not significantly correlated with magnitude of cortisol responses, although trends for inverse correlations were observed. (6) It is suggested that these normal diurnal differences in the acute cortisol response to amphetamine may be related to a corresponding rhythm in the responsitivity to amphetamine of neuroendocrine neurotransmitters. (7) The previously reported abnormal cortisol response to amphetamine in a group of endogenous depressives probably is not primarily related to variables of age, sex or baseline cortisol level.