Cortisol secretion and dexamethasone response in depression

The authors administered 2 mg of dexamethasone at 11:00 p.m. to 37 unmedicated hospitalized endogenously depressed patients and assessed their plasma cortisol response at 4:00 and 11:00 p.m. the next day. In addition, on nondexamethasone days 26 of these patients had mean 24 hour plasma cortisol concentration determinations from samples taken at 30 min intervals and 32 had plasma determinations from a single sample taken at 4:00 and 11:00 p.m. Mean 24-hour plasma cortisol concentration was elevated in 50%; only 7 of the 26 were dexamethasone resistant, and 6 of these 7 were hypersecretors. The authors suggest that dexamethasone resistance reflects the abnormality of cortisol hypersecretion in depression and that the 2-mg dexamethasone suppression test is a highly specific but not very sensitive indicator of hypersecretion.