Prostate specific antigen

Psa is a protein made in the prostate gland that functions to liquefy sperm. It is a serine protease made by both normal and malignant prostate glands. Commonly used as a screening test for prostate cancer, the psa test is widely used to detect which men would benefit from a prostate biopsy as well as detect cancer recurrence in men who have been treated for prostate cancer.