total prostate-specific antigen (PSA)

General Information

Prostate Specific Antigen (PSA) - Glycoprotein with protease activity. It is synthesized in the cells of the prostate epithelium and secreted into the seminal fluid, which ensures the liquefaction of sperm. PSA is present in minimal amounts in the blood and is found in both free (free PSA) and associated forms of α1-antichymotrypsin (PSA-ACT) and α2-macroglobulin (PSA-AMG). 86% of circulating PSA is represented as PSA-ACT complex, only a small fraction of PSA is associated with α2-macroglobulin and is not detected in laboratory studies, therefore the total PSA level determined is the sum of free PSA and PSA-ACT complex. . With age, total PSA levels increase and the percentage of free PSA decreases.