Laboratory professionals in the lab checking prostate-specific antigen

What Is A Prostate-Specific Antigen?

Medically reviewed on June 27, 2022 by Jordan Stachel, M.S., RDN, CPT. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.

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Aside from skin cancers, prostate cancer is the leading cancer among men in America. Estimates suggest that one in eight men will receive a prostate cancer diagnosis at some point in his life. It typically affects older men with about 6 out of 10 diagnoses affecting men 65 and older. It’s rare in men younger than 40, but it’s not implausible [1].

Prostate cancer is the second leading cause of death among men in America, just behind lung cancer. The good news is that many men who have been diagnosed with prostate cancer are still alive and well today [1].

A prostate cancer treatment can also be considered, though success is determined by how early the cancer is found. An increasingly common blood test for screening is the prostate-specific antigen (PSA) test, and PSA testing is integral for early diagnosis. Learn more about the prostate-specific antigen below.

What Is the Prostate?

The prostate is a small gland located in front of the rectum and below the bladder. This walnut-shaped gland is only found in people assigned male at birth, and it primarily plays a role in creating some of the seminal fluid that transports and nourishes sperm cells. The seminal vesicles, located just behind the prostate gland, make most of the fluid that makes up semen. The urethra passes through the center of the prostate gland and carries urine and semen out of the body via the penis [2]. In some cases, health problems can occur in the prostate such as prostate cancer and benign prostatic hyperplasia.

What is Prostate Cancer?

The prostate can potentially suffer numerous problems. For example, the size of the prostate can change as you age. While it typically starts at the size of a walnut, it can potentially get bigger. An enlarged prostate can lead to other health problems, like problems urinating, but this typically does not increase the risk of cancer [3].

Prostate cancer refers to any cancer that originates within the cells of the prostate gland. Nearly all forms of prostate cancer are adenocarcinomas, meaning that they develop in the gland cells. These are the cells that make the fluid that goes into semen [2]. Most forms of prostate cancer progress slowly and don’t grow beyond the prostate, requiring minimal treatment (or potentially no treatment at all). However, some cases of prostate cancer can progress quickly and aggressively, easily spreading to other parts of the body [4].

Common signs and symptoms of prostate cancer include:

  • Urinating problems
  • Blood in the urine or semen
  • Less pressure in the urine stream
  • Erectile dysfunction
  • Unintentional weight loss
  • Pain in the bones

However, prostate cancer typically doesn’t present any noticeable symptoms in its early stages, which makes screening incredibly important [4].

Understanding Prostate-Specific Antigen Tests

Cells in the prostate gland make a special protein called “prostate-specific antigen.” While this antigen primarily appears in semen, smaller amounts of it can be found in the blood [5]. A PSA test result may come back with a high PSA level, which may indicate prostate cancer, infection, inflammation, or an enlarged prostate. Both normal and cancerous cells make this protein, so the more cells creating prostate-specific antigen, the more it may contribute to it in the blood [6].

PSA measurement is done in nanograms per milliliter. While an elevated PSA level may indicate a higher chance of prostate cancer, there is no specific cutoff point that indicates that there may be prostate cancer. Most healthcare providers consider a PSA level of 4 ng/mL or more as an indication that you may need further testing. Others may set that level at 2.5 or 3 ng/mL [5].

Most people without prostate cancer have a prostate-specific antigen level below 4 ng/mL. As your prostate cancer progresses, your PSA levels will typically go above 4 ng/mL. PSA levels between 4 and 10 ng/mL typically indicate about a one in four chance of having prostate cancer. PSA levels over 10 ng/mL may indicate up to a 50 percent chance of having prostate cancer. However, PSA levels under 4 ng/mL do not guarantee that there is no cancer [5].

What Else Affects Your Prostate-Specific Antigen Levels?

Part of what makes it difficult to set a cutoff point is that there are numerous variables that can increase PSA levels. This can include:

  • An enlarged prostate
  • Older age
  • Prostatitis (inflammation or infection of the prostate gland)
  • Some medication (like testosterone)
  • Some urologic procedures that affect the prostate [5]

Ejaculation can also increase your prostate-specific antigens in the short term. Your healthcare provider may suggest abstaining from sex prior to the test. Some studies also suggest that riding a bike may increase PSA levels [5].

Other factors that can decrease your prostate-specific antigen levels include:

  • 5-alpha reductase inhibitors
  • Herbal mixtures taken as dietary supplements
  • Long-term use of aspirin, thiazide diuretics, statins, and other medicines [5]

It’s important to understand that PSA levels can be low even if there is prostate cancer. It’s worth talking with your healthcare provider about anything that might be affecting your PSA levels [5].

Abnormal Prostate-Specific Antigen Results

Prostate-specific antigen tests should not be used on their own as a diagnostic tool. If PSA test results come back higher than normal or are at an otherwise abnormal level, it does not automatically mean that there is prostate cancer or a prostate issue. As mentioned above, there are numerous things that can cause high PSA levels. However, if the test does come back with abnormal results, you will need to go through further testing and examination to determine if there is a prostate problem [5]. This may include:

  • Taking a second prostate-specific antigen test later
  • Getting a digital rectal exam (DRE) or other test
  • Getting a prostate biopsy [5]

A prostate biopsy is often the best way to determine if there is prostate cancer, particularly if PSA levels are abnormal. A biopsy involves taking small tissue samples from the prostate. The process involves inserting hollow needles into the prostate and removing a tissue sample. The needles are usually inserted into the rectal walls, known as a “transrectal biopsy.” Your provider may also use ultrasound to see the prostate during the biopsy [7].

These samples are then examined and tested to determine the presence of cancerous cells. A biopsy can also determine the extent of the cancer and how likely the cancer will spread [5].

Once your provider has diagnosed the prostate, they can determine treatment options. Some earlier forms of prostate cancer may not even need treatment beyond active surveillance to make sure the cancer does not worsen or spread. Other forms of treatment include radiation therapy, hormone therapy, and chemotherapy. Your healthcare provider may also recommend surgery to remove the prostate and some of the surrounding tissue [6].

Learn more about how to check your prostate health, and how to improve your prostate health on our blog.

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1. Key Statistics for Prostate Cancer. American Cancer Society. URL. Accessed June 27, 2022.

2. What Is Prostate Cancer? American Cancer Society. URL. Accessed June 27, 2022.

3. Enlarged prostate. Medline Plus. URL. Accessed June 27, 2022.

4. Prostate cancer. Mayo Clinic. URL. Accessed June 27, 2022.

5. Screening Tests for Prostate Cancer. American Cancer Society. URL. Accessed June 27, 2022.

6. Prostate cancer. Mayo Clinic. URL. Accessed June 27, 2022.

7. Prostate-Specific Antigen (PSA) Test. NIH. URL. Accessed June 27, 2022.

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