What is the Origin of Free Testosterone Assay?

The need for this assay arose from the clinical observation that total testosterone levels alone often do not correlate perfectly with the symptoms of androgen deficiency. It is based on the endocrinological principle of hormone bioavailability, recognizing that only the unbound steroid can easily diffuse into target cells.

What is the Mechanism of Free Testosterone Assay?

Highly accurate methods, such as equilibrium dialysis or mass spectrometry, physically separate the free testosterone from the bound fraction for direct measurement. Less precise methods use calculated estimates based on total testosterone and SHBG levels. The resulting value provides a crucial index of androgenic status, guiding the diagnosis and therapeutic titration in hormonal health.

Free Testosterone Assay

Meaning

A Free Testosterone Assay is a specific laboratory test used to quantify the concentration of biologically active, unbound testosterone circulating in the bloodstream. This measurement is distinct from total testosterone, which includes hormone bound to Sex Hormone-Binding Globulin and albumin. The free fraction is the portion immediately available to bind to androgen receptors and exert its physiological effects.