Prostate-specific Antigen (PSA) is a glycoprotein enzyme produced by the epithelial cells of the prostate gland. This test measures PSA levels in the blood, which serves as a tumor marker for prostate cancer screening and monitoring. PSA is normally secreted into the prostatic ducts and seminal fluid, with only small amounts entering the bloodstream. Elevated PSA levels can indicate various prostate conditions including prostate cancer, benign prostatic hyperplasia (BPH), prostatitis, or prostate trauma. While PSA testing is valuable for early detection of prostate cancer, it is not diagnostic on its own and must be interpreted in conjunction with clinical evaluation, digital rectal examination, and other diagnostic procedures. The test is also used to monitor treatment response in men with prostate cancer and detect disease recurrence after therapy. PSA levels can be affected by various factors including age, prostate size, recent procedures, and certain medications.