Prostate-specific antigen (PSA) is produced almost exclusively by prostate cells. It screens for and monitors prostate cancer and detects BPH and prostatitis. PSA is not cancer-specific — BPH, prostatitis, ejaculation, and instrumentation all elevate it, making clinical context essential.

PSA screening is a shared decision between patient and clinician, weighing early cancer detection benefits against overdiagnosis risk. Serial PSA measurements are more informative than a single result.