Prostate-Specific Antigen (PSA)
PSA is a glycoprotein made almost exclusively by the prostate. Elevations can mean cancer, benign enlargement, prostatitis or recent ejaculation — the test is sensitive but not specific.
What it measures
PSA is produced by prostate epithelial cells and liquefies semen. A small amount leaks into the bloodstream normally; conditions that disrupt prostate architecture leak more. PSA has been used for prostate-cancer screening since the 1990s, but the test has limitations — it's elevated in benign prostatic hyperplasia, prostatitis and even temporarily after ejaculation, cycling or digital rectal exam. Modern guidelines have moved away from universal screening toward shared decision-making with age- and risk-adjusted thresholds. The PSA velocity (rate of change) and PSA density (relative to prostate volume) often matter more than the absolute value.
What a high value can mean
- Benign prostatic hyperplasia (BPH) — the most common reason; PSA rises gradually with prostate volume.
- Prostatitis — bacterial or chronic; PSA can rise dramatically and normalise over weeks.
- Prostate cancer — risk rises with PSA level but the relationship is non-linear; many men with elevated PSA don't have cancer.
- Recent ejaculation, vigorous cycling, digital rectal exam — short-term rises.
- Urinary tract infection, urinary retention — transient.
What a low value can mean
- Generally reassuring — low PSA correlates with lower prostate-cancer risk.
- 5α-reductase inhibitors (finasteride, dutasteride) — drop PSA by ~50%; double the measured value when interpreting.
When to discuss with a doctor
Elevated PSA on screening should not lead directly to biopsy — most guidelines now recommend a repeat PSA in 4–8 weeks, free/total PSA ratio, and multiparametric prostate MRI before invasive procedures. Persistent elevation or rapid velocity warrants urology referral. Men aged 50–69 (45–50 if family history or African ancestry) should discuss the screening decision with their primary-care doctor. Mediora.AI logs PSA values over time so velocity is visible.