What is the Origin of Bioavailable Androgen Levels?

This term developed in clinical endocrinology to address the limitations of total hormone testing, recognizing that SHBG-bound hormones are largely inert. The concept is a practical compromise between measuring only the very small free fraction and the often misleading total level. It offers a clearer picture of the hormone available for biological effect.

What is the Mechanism of Bioavailable Androgen Levels?

Albumin-bound androgens, unlike SHBG-bound androgens, bind weakly enough to dissociate readily at the capillary level, making them biologically available to diffuse into target cells. The measurement, often determined via calculation using total testosterone, albumin, and SHBG values, reflects this dynamic equilibrium. Adequate bioavailable levels are essential for maintaining muscle mass, bone density, libido, and neurocognitive function by ensuring sufficient ligand is present to activate androgen receptors.

Bioavailable Androgen Levels ∞ Area

Bioavailable Androgen Levels

Meaning

Bioavailable Androgen Levels quantify the circulating concentration of androgens, predominantly testosterone and dihydrotestosterone (DHT), that are loosely bound to albumin and the small fraction that is completely unbound (free). This combined measurement represents the pool of hormone that can easily dissociate from binding proteins and become accessible to target tissues. This metric is a more accurate clinical indicator of androgen action than total testosterone, especially when Sex Hormone-Binding Globulin (SHBG) levels are abnormal.