Transport of Steroid Hormones: Binding of 21 Endogenous Steroids to Both Testosterone-Binding Globulin and Corticosteroid-Binding Globulin in Human Plasma

Key Points

• To determine the binding affinities of 21 endogenous steroids for plasma transport proteins and computationally model their distribution in various physiological states.
• Measured binding affinities of 21 endogenous steroids to testosterone-binding globulin (TeBG) and corticosteroid-binding globulin (CBG) via a solid-phase method at physiological pH and temperature.
• Applied a computer model to calculate multi-ligand equilibrium binding across TeBG, CBG, and albumin.
• Quantified steroid distribution into TeBG-bound, CBG-bound, albumin-bound, and free fractions in healthy men, women during follicular and luteal phases, and third-trimester pregnant women.
• Established a comprehensive mathematical model resolving complex competitive binding interactions among 21 steroids and three major plasma transport proteins.
• Determined specific fractional distributions of bound and unbound steroids across distinct physiological states, including the menstrual cycle and late pregnancy.