Corticosteroid-binding globulin: Modulating mechanisms of bioavailability of cortisol and its clinical implications

Corticosteroid-binding globulin (CBG) is the principal transport protein of glucocorticoids. Approximately 80–90% of serum cortisol binds to CBG with high affinity and only about 5% of cortisol remain unbound and is considered biologically active. CBG seems to modulate and influence the bioavailability of cortisol to local tissues. In this review, we will discuss physicochemical properties of CBG and structure of CBG in the mechanisms of binding and release of cortisol. This review describes several factors affecting CBG functions, such as genetic factors or temperature. Furthermore, clinical implications of CBG abnormalities and the measurement of CBG and its use for assessment of free cortisol levels are described in this review.