PSA, Free Unit Converter

Free PSA is the portion of prostate-specific antigen (PSA) in your blood that is not bound to proteins. Unlike the majority of PSA, which circulates attached to alpha-1-antichymotrypsin and other protease inhibitors, free PSA floats unbound in the bloodstream.

PSA is a glycoprotein enzyme produced by prostate cells that helps liquefy semen. Normally, only small amounts enter the bloodstream. When prostate conditions develop, more PSA leaks into circulation in both free and bound forms.

Free PSA typically represents a small fraction of total PSA. When measured alongside total PSA, it helps clinicians distinguish between benign prostate conditions and prostate cancer, particularly when total PSA falls in the borderline range of 4.0 to 10.0 ng/mL.

Free PSA is produced by the epithelial cells of the prostate gland. It is also made in small amounts by the lining of the urethra and the bulbourethral glands. In men with a normal prostate, most free PSA in serum represents inactive PSA that has been cleaved internally before entering the bloodstream.