What Is PSA? - Definition, Test & Normal Levels

Instructor: Justine Fritzel

Justine has been a Registered Nurse for 10 years and has a Bachelor's of Science in Nursing degree.

In this lesson, we will learn about the prostate gland in men. We will briefly discuss prostate cancer and review how to screen for prostate cancer with the use of PSA testing.

Prostate Cancer

Prostate cancer is very common, perhaps you have known someone who has had it. American men have a 14% chance of being diagnosed with prostate cancer during their lifetime. The prostate is a gland near the bladder in males that produces some of fluid contained in semen. Prostate cancer is when cells of the prostate gland grow out of control.

In 2013, it was estimated that about 2.8 million men in the United States had prostate cancer. In this lesson we'll talk about a way doctors can screen for it.

PSA Tests

The prostate gland is about the size of a walnut in younger males.
prostate gland

The prostate gland produces a protein called prostate specific antigen (PSA). Most of the PSA is removed from the body with semen, but some of it ends up in the blood stream. Normally, this is a very small amount that is either free floating or bound to other substances.

The PSA test refers to a blood test that measures both free and bound PSA produced by the body. When you hear the term 'total PSA' in regards to blood test results, it refers to the free and bound PSA combined.

The PSA blood test can be used to screen for prostate cancer, assess how aggressive the cancer is, monitor treatment, or identify a recurrence.

PSA Levels

High PSA levels in a man does not necessarily mean that he has or will develop prostate cancer. As men age, it is common for the prostate gland to increase in size, called benign prostate hypertrophy or BPH. Inflammation of the prostate, called prostatitis, is also common. Both of these conditions can increase PSA levels, but do not necessarily point to cancer.

Normal PSA levels will be higher the older the man is. Laboratories typically identify the highest normal level of PSA to be 4ng/mL (nanograms per milliliter). Age-specific normal levels are:

  • 2.5 ng/mL for males age 40-49
  • 3.5 ng/mL for males age 50-59
  • 4.5 ng/mL for males age 60-69
  • 6.5 ng/mL for males age 70-79

If the PSA is being used for screening, a level between 4 to 10 ng/mL would indicate further testing is needed. Most men with these levels will not have prostate cancer, but as the level rises above 10 ng/mL the likelihood of cancer greatly increases. If a man's PSA level rises quickly during the year before diagnosis is made, he has a higher risk of death even despite treatment.

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