What is the Origin of Serum Free Testosterone?

The term is derived from 'serum,' the liquid component of blood minus clotting factors, and 'free,' indicating lack of binding affinity to carrier proteins like Sex Hormone-Binding Globulin (SHBG). In clinical endocrinology, its measurement is essential for diagnosing hypogonadism accurately, especially when SHBG levels are abnormal. This metric directly reflects the hormone available for anabolic and reproductive signaling.

What is the Mechanism of Serum Free Testosterone?

The mechanism involves calculating or directly measuring the fraction of testosterone not complexed with SHBG or albumin, often through equilibrium dialysis or validated immunoassay methods. High levels of SHBG effectively sequester testosterone, reducing the biologically available pool even if total levels appear adequate. Therefore, the concentration of free testosterone dictates the magnitude of downstream androgen receptor activation across various tissues.

Serum Free Testosterone

Meaning

Serum Free Testosterone represents the concentration of biologically active, unbound testosterone circulating in the bloodstream, which is available to interact with androgen receptors in target tissues. Only this unbound fraction exerts physiological effects, unlike total testosterone which includes protein-bound components. Measuring this value provides a superior assessment of androgen status than total testosterone alone.