Cortisol secretion in endogenous depression. I. Basal plasma levels.

Plasma levels of cortisol were sampled for 24 hours in 32 endogenously depressed (ED) patients and 72 normal controls who also underwent the dexamethasone suppression test. The ED patients had significantly higher mean 24-hour plasma levels of cortisol (means 24h PC). However, means 24h PC values of subjects in both groups were normally distributed, with a marked overlap between the two. Only seven ED patients had means 24h PC values higher than 2 SDs from the normal mean (greater than 10 micrograms/dL). An abnormal dexamethasone suppression test result was only partially related to basal cortisol levels. The mean plasma level of cortisol between 1 and 4 PM was found to be highly correlated with the means 24h PC value in ED patients, as has been previously reported in normal subjects and patients with various other diseases (in which it also powerfully discriminated between hypersecretors and normosecretors). This finding supports the use of mean cortisol levels between 1 and 4 PM as a reliable and convenient indication of cortisol secretion.