The Free Hormone Hypothesis: When, Why, and How to Measure the Free Hormone Levels to Assess Vitamin D, Thyroid, Sex Hormone, and Cortisol Status.

ABSTRACT: The free hormone hypothesis postulates that only the nonbound fraction (the free fraction) of hormones that otherwise circulate in blood bound to their carrier proteins is able to enter cells and exert biologic effects. In this review, I will examine four hormone groups-vitamin D metabolites (especially 25OHD), thyroid hormones (especially thyroxine [T4]), sex steroids (especially testosterone), and glucocorticoids (especially cortisol)-that are bound to various degrees to their respective binding proteins-vitamin D-binding protein (DBP), thyroid-binding globulin (TBG), sex hormone-binding globulin (SHBG), and cortisol-binding globulin (CBG)-for which a strong case can be made that measurement of the free hormone level provides a better assessment of hormonal status than the measurement of

SUBMITTER: Bikle DD 

PROVIDER: S-EPMC7839820 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature