What is the Origin of Circulating Androgen Fractions?

This terminology arose from the development of advanced laboratory assays in endocrinology, which allowed for the precise separation and quantification of steroid hormones based on their protein-binding characteristics. The recognition of SHBG's regulatory role led to the differentiation of these distinct fractions.

What is the Mechanism of Circulating Androgen Fractions?

Androgens are lipophilic hormones that travel in the circulation largely bound to carrier proteins, predominantly SHBG and albumin. Only the unbound, or "free," fraction, along with the albumin-bound portion (which dissociates easily), is considered biologically active, capable of diffusing across cell membranes to interact with intracellular androgen receptors. The concentration of SHBG acts as a critical modulator, directly influencing the amount of free and bioavailable testosterone available to target tissues.

Circulating Androgen Fractions ∞ Area

Circulating Androgen Fractions

Meaning

Circulating Androgen Fractions refers to the different molecular forms of androgen hormones, such as testosterone and dihydrotestosterone (DHT), present in the bloodstream, categorized by their binding status to plasma proteins. These fractions include the biologically inert Sex Hormone-Binding Globulin (SHBG)-bound fraction, the loosely bound albumin fraction, and the highly bioavailable free fraction. Clinically, assessing these fractions provides a more nuanced picture of androgen status than total levels alone.