What is the Origin of Free Testosterone Range?

This clinical term is derived from the biochemical analysis of steroid hormones, distinguishing between total testosterone and its various binding states. The concept of "free" hormone is central to understanding bioavailability and pharmacological effect.

What is the Mechanism of Free Testosterone Range?

Testosterone is synthesized primarily by the gonads and adrenal glands, entering the circulation where most is bound to transport proteins, predominantly SHBG. The free fraction, typically less than 2% of total testosterone, is the portion that interacts with androgen receptors inside target cells to initiate genomic and non-genomic signaling. This free level is inversely correlated with SHBG concentration and is the true determinant of androgenic action.

Free Testosterone Range ∞ Area

Free Testosterone Range

Meaning

The Free Testosterone Range represents the concentration of biologically active, unbound testosterone in the serum that is available to diffuse into target tissues and exert its physiological effects. This fraction is not bound to Sex Hormone-Binding Globulin (SHBG) or albumin, making it the most clinically relevant measure for assessing androgen status and tissue effect. Maintaining levels within an optimal, rather than merely “normal,” range is essential for metabolic, sexual, and cognitive health.