PSA, also known as prostate specific antigen, describes a glycoprotein produced in the prostate gland. PSA acts as an enzyme and helps to keep the seminal fluid in liquid form therefore aiding in sperm movement. Although most PSA remains in the ducts of the prostate, a small amount leaks into the bloodstream, allowing doctors to use PSA as a marker for the detection of prostate diseases, especially prostate cancer. Because many factors affect PSA levels, including age, doctors can utilize age-specific PSA levels to determine if further testing should be done.
The prostate gland, a male reproductive gland, resides below the bladder and in front of the rectum. The prostate surrounds the urethra, which allows it to perform its main function of squeezing fluid into the urethra during sexual climax to not only help sperm move, but also to protect and nourish the sperm, according to the PSA Rising website. The interior of the prostate gland contains a layer of epithelial cells, which produce the PSA, surrounded by a layer of basal cells and a basement membrane.
Prostate Cancer and PSA
Normally the body regulates the growth of cells, creating new cells to replace old cells when they die. When this process becomes interrupted, new cells may continue to form even when not needed or old cells may fail to die, creating a mass, or tumor, known as cancer. Prostate cancer occurs when a tumor originates in the cells inside the prostate. Because of the added number of cells, the prostate produces increased levels of PSA. In addition, the tumor disrupts the normal structure, moving the basal layer and basement membranes, which allows more PSA to leak into the blood, as described in a study published by Balk and associates in the January 2003 issue of "Journal of Clinical Oncology."
Abnormal PSA Levels
Because prostate cancer is the second most common type of cancer in men, according to the National Cancer Institute, and the second leading cause of cancer death, doctors strive to detect prostate abnormalities early. The U.S. Food and Drug Administration approve the use of the PSA test along with a digital rectal exam to detect prostate cancer in men over the age of 50, according to the National Cancer Institute. In general, doctors consider a result of 4 nanograms/milliliter of blood as abnormal, prompting them to perform additional testing.
Age and PSA
Although elevated PSA levels may indicate prostate cancer, a result of 4 ng/mL does not conclusively diagnose the presence of cancer. In addition, men under the age of 50 can develop prostate cancer and their PSA levels may register less than 4 ng/mL. In fact, the "Journal of Clinical Oncology" reports that 20 to 50 percent of prostate cancer cases occur in men with PSA levels less than 4 ng/mL.
Age-Specific PSA Levels
To increase cancer detection in younger men, doctors created age-specific ranges for abnormal PSA readings. The Memorial Sloan-Kettering Cancer Center reports that age-specific PSA ranges as greater than 2.5 ng/mL for ages up to 49, greater than or equal to 3.5 ng/mL for ages 50 to 59, and greater than or equal to 4.0 ng/mL for men 60 or older.
- PSA Rising: Prostate
- "Journal of Clinical Oncology": Biology of Prostate Specific Antigen; Balk et. al.; 2003
- National Cancer Institute: What You Need to Know About Prostate Cancer
- National Cancer Institute: Understanding Prostate Changes
- Memorial Sloan-Kettering Cancer Center: Prostate Cancer Screening Tests