Abstract
In a method for the simultaneous determination of cortisone, cortisol, and corticosterone, the extracted steroids are separated using paper chromatography and assayed by competitive protein binding. Evidence of the reliability of the method, particularly with respect to the determination of cortisone, is presented. Only trivial changes in cortisone level were detected in response to exercise, surgery, and ACTH, even though marked changes in cortisol level were simultaneously recorded. It is suggested that the inertia in plasma cortisone level may be related to its lesser degree of binding to plasma proteins, relative to cortisol, which would permit more rapid hepatic uptake and possible accumulation of a large extravascular pool of cortisone.