Transcortin

Overview
Transcortin, also corticosteroid-binding globulin or CBG, is officially called serpin peptidase inhibitor, clade A (alpha-1 antiproteinase, antitrypsin), member 6.

It is an alpha-globulin.

Binding
Transcortin binds several proteins:


 * Cortisol. Approximately 75% of the cortisol in circulation is bound to this plasma protein. (The rest is bound to serum albumin.) The cortisol is thought to be biologically active only when it is not bound to transcortin.


 * Aldosterone. 60% of the aldosterone in blood is bound to this plasma protein.


 * Progesterone

Production
Transcortin is produced by the liver and is regulated by estrogens. Therefore, plasma transcortin levels increase during pregnancy, and are decreased in cirrhosis.