What is the Origin of Free Testosterone Fraction Analysis?

The necessity for this specific analysis arose from the realization in endocrinology that total hormone levels often do not reflect true biological activity due to variable levels of Sex Hormone-Binding Globulin (SHBG) and albumin. The concept of the "free fraction" as the active component dates back to the mid-20th century, refining the clinical assessment of hormonal status. This measurement provides a more accurate index of androgen action.

What is the Mechanism of Free Testosterone Fraction Analysis?

Testosterone circulates primarily bound to SHBG and, to a lesser extent, albumin; only about 1-3% remains unbound as the free fraction. The mechanism of analysis involves laboratory techniques like equilibrium dialysis or calculated indices to separate and measure this small, active component. Assessing this fraction directly correlates with androgen receptor saturation and is a superior biomarker for evaluating symptoms of hypogonadism compared to total testosterone alone.

Free Testosterone Fraction Analysis

Meaning

Free Testosterone Fraction Analysis is a specialized laboratory measurement that quantifies the concentration of biologically active, unbound testosterone in the circulation. This fraction represents the testosterone immediately available to interact with target tissues and exert androgenic effects, unlike total testosterone, which includes the protein-bound portion. Clinical interpretation of this metric is essential for accurately diagnosing and managing androgen deficiency states.