Serpin Peptidase Inhibitor, Clade A, Member 6 (SerpinA6) belongs to the Serine Protease Inhibitors superfamily. SerpinA6 is synthesized in liver and has also been identified in a number of glycocorticoid responsive cells. SerpinA6 has an alpha-globulin protein with corticosteroid-binding properties. It is the major transport protein for glucocorticoids and progestins in the blood of most vertebrates. Defects in SERPINA6 are a cause of corticosteroid-binding globulin deficiency which is an extremely rare hereditary disorder characterized by reduced corticosteroid-binding capacity with normal or low plasma corticosteroid-binding globulin concentration, and normal or low basal cortisol levels associated with hypo/hypertension and muscle fatigue.