What is the Origin of Free T Assays?

This is a technical term used in clinical chemistry and endocrinology, where "Free T" is the abbreviation for free testosterone and "Assays" refers to the analytical method of quantification. The need for these specialized tests arose from the clinical realization that total testosterone levels alone often fail to reflect the true biological availability of the hormone, especially when SHBG levels are aberrant.

What is the Mechanism of Free T Assays?

The most reliable assays, such as equilibrium dialysis or mass spectrometry, physically separate the free testosterone from its binding proteins before measurement, offering a direct quantification. Alternatively, calculated free testosterone (cFT) methods utilize measured total testosterone and SHBG values in a mathematical formula to estimate the free fraction. The result directly indicates the amount of hormone available to activate the androgen receptors in muscle, bone, and brain tissue.

Free T Assays

Meaning

Laboratory diagnostic procedures specifically employed to accurately quantify the concentration of testosterone that is not bound to carrier proteins, particularly Sex Hormone-Binding Globulin (SHBG) and albumin. This unbound fraction, known as free testosterone, is the biologically active portion of the hormone that can freely diffuse into target cells to exert its effects. Clinically, this measurement provides the most direct and functional assessment of androgen status.