Definition of "PSA"

Last modified: 18 hours



PSA (prostate-specific antigen, aka gamma-seminoprotein, kallikrein-3 KLK3) is an enzyme secreted by epithelial cells of the prostate gland.

Patient information

I know PSA is a test for prostate cancer, but, what is it exactly?
PSA is an enzyme that's secreted by the prostate.

What's the prostate?
It's apart of the male reproductive system. It secretes an alkaline milky, white fluid, that constitutes about 30% of semen. The alkalinity of semen, helps neutralize the acidity of the vaginal tract, therefore prolonging the lifespan of sperm.

Pathophysiology
  • Produced for the ejaculate, where it liquefies semen in the seminal coagulum and allows sperm to swim freely
  • Also instrumental in dissolving cervical mucus, allowing the entry fo sperum into the uterus
  • Present in small quantities in the serum of men w/ healthy prostates, but is often ELEVATED in the presence of prostate cancer, or other prostate disorders

Patient information

So what happens in prostate cancer?
Since the prostate secretes PSA, if it has cancer, it's going to secrete lots of PSA. So it will be elevated in prostate cancer, as well as in other prostate disorders.

Indications
  • Cancer → only 30% of Pt's with high PSA, are Dx w/ prostate cancer after biopsy
  • Problematicaly, can also detect:
    • Prostatitis
    • Benign prostatic hyperplasia

Patient information

So having a high PSA, can mean things other than cancer?
Yes, it can also mean inflammation of the prostate. Or even a big prostate.

Epidemiology
  • USA doesn't recommend PSA screening, noting testing may result in over-Dx and over-Tx, because most prostate cancer is asymptomatic for life, and Tx involves risks of complications including impotence (erectile dysfunction) and incontinence concluding that benefits don't outweigh harms

Patient information

Isn't it a bit of an issue that PSA can be high, in things other than prostate cancer?
It is, which is why the USA doesn't recommend PSA screening, because the risks outweigh the benefits. This is particularly the case if there are no risk factors that are present.

See also
  • Tumor marker (category)

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Definition of PSA | Autoprac


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