Episodic variation in plasma corticosteroids in subjects with Cushing's syndrome of differing etiology.

The concentration of plasma corticosteroids was determined every 20 min during a period of 26 hr in 3 normal subjects and in 7 patients with Cushing's syndrome of differing etiology. In all the patients with hypercorticalism, the plasma corticosteroids were elevated and clearly differed in their nycthemeral rhythmicity from normal, but no discrimination could be made in this parameter between patients with pituitarydependent or independent Cushing's syndrome, or those associated with the ectopic production of ACTH.