A combined study of cortisol, ACTH and dexamethasone concentrations in major depression. Multiple time-point sampling.

The pathophysiology of hypercortisolaemia in major depression was examined. ACTH was measured using a novel immunoradiometric assay of high specificity and sensitivity. Twenty-eight patients with major depression and 18 control subjects were studied. Blood samples for basal hormone concentration were taken at 09:00, 16:00 and 23:00 on day 1, followed by administration of 1 mg dexamethasone at 23:00. Further samples were taken at 09:00 and 16:00 on day 2. Dexamethasone concentration was measured in day 2 samples and no significant difference was found between the depressed group and control subjects. In the depressed group cortisol concentration was elevated at 23:00 on day 1, and ACTH concentrations were elevated in post-dexamethasone samples. ACTH and cortisol concentrations were not directly correlated in individual patients. The elevated plasma cortisol associated with major depression is not solely mediated by changes in ACTH.