Pituitary-adrenal axis rhythm disturbances in psychiatric depression

We studied disturbances in the circadian pattern of plasma corticotropin and cortisol concentrations in 25 depressed patients (eight dexamethasone suppression test [DST] nonsuppressors and 17 suppressors) and 21 normal control subjects. Blood samples were drawn every 20 minutes for 24 hours before the administration of dexamethasone, and for a second 24 hours after the administration of 1 mg of dexamethasone. The corticotropin and cortisol level rhythms were examined using three different statistical methods. Nonsuppressors averaged greater elevations in plasma cortisol and corticotropin levels than did subjects in the other two groups, both before and after administration of the dexamethasone. The cortisol levels of the suppressors were virtually identical to those of the control subjects. However, the suppressors had significant elevations of corticotropin levels compared with normal control subjects, especially on the day before taking dexamethasone. Before taking dexamethasone, the depressed patients reached a daily nadir of cortisol concentration approximately two hours earlier than did the normal control subjects. The DST nonsuppressors also exhibited a blunting in the expected circadian rhythm of the corticotropin level.