Free testosterone

CALCULATED FREE TESTOSTERONE

The majority of testosterone in the blood is bound to proteins. Approximately two-thirds of the testosterone in the blood is SHBG-bound and slightly less than one third is bound to albumin. A small percentage of testosterone (2–4 %) circulates freely in the blood. Free testosterone and albumin-bound testosterone represent bioavailable testosterone that can affect the target tissue. Calculating free testosterone provides more information about the biological activity of an individual's testosterone production.

Reference ranges for highly sensitive free testosterone:

• Women: 5–23 pmol/L
• Men: 230–575 pmol/L