Cortisol Transport and Disappearance

Abstract

Reversible binding of cortisol plasma proteins is fundamental in controlling the availability of secreted or administered cortisol to tissues and in protecting it from inactivation or excretion. At usual physiologic levels, plasma cortisol is bound predominantly by an alpha-globulin (corticosteroid-binding globulin, CBG, transcortin). At even slightly elevated plasma levels, the binding capacity of CBG becomes saturated, and cortisol is bound predominantly but loosely by a portion of plasma albumin (corticosteroid-binding albumin, CBA). Unbound, physiologically active cortisol comprised only 10% of the total cortisol present in morning plasma samples of 50 normal individuals. Because of the observed binding constants of cortisol