What is the Origin of Cortisol-Binding Globulin?

The protein was first identified and characterized in the mid-20th century as researchers sought to understand how steroid hormones, which are largely hydrophobic, are transported efficiently through the aqueous environment of the blood. Its discovery highlighted the sophisticated regulatory mechanisms governing steroid hormone action beyond simple glandular secretion.

What is the Mechanism of Cortisol-Binding Globulin?

CBG's mechanism is one of sequestration and controlled release. It possesses a high affinity for cortisol, forming a complex that renders the hormone biologically inactive while in circulation. This bound reservoir protects cortisol from rapid metabolic clearance and provides a stable pool. The local release of cortisol at target tissues can be facilitated by proteolytic cleavage of CBG, a process often triggered by inflammatory mediators, ensuring hormone availability precisely where and when it is needed.

Cortisol-Binding Globulin ∞ Area

Cortisol-Binding Globulin

Meaning

Cortisol-Binding Globulin (CBG), also known as transcortin, is a plasma glycoprotein synthesized primarily by the liver that serves as the principal transport protein for cortisol and, to a lesser extent, progesterone in the bloodstream. By binding the majority of circulating cortisol, CBG regulates the concentration of the biologically active, unbound “free” cortisol fraction available to target tissues. Changes in CBG levels, often influenced by estrogen status or thyroid function, significantly alter the bioavailability of the stress hormone cortisol, impacting the hypothalamic-pituitary-adrenal (HPA) axis.

A precise cellular network radiates from a central core, symbolizing the intricate endocrine system's homeostasis. This visualizes bioidentical hormone replacement therapy HRT's complex feedback loops, emphasizing hormonal balance, metabolic optimization, and cellular health in personalized medicine for longevity.

What Are the Long-Term Effects of Hormonal Optimization on Adrenal Health?

Hormonal optimization recalibrates the body's endocrine network, requiring a responsive adaptation from the adrenal system to maintain long-term equilibrium.

∞ Clinical Monitoring
∞ Estrogen Replacement Therapy
∞ Steroidogenesis