Prostate specific antigen, or PSA, is a protein secreted by the epithelial cells in the prostate gland. The prostate is a male reproductive gland that produces approximately one-third of the fluid in the semen a man ejaculates, according to PSA Rising. Although most PSA moves into the ducts of the prostate gland, some leaks into the bloodstream. Because conditions like prostate cancer and an enlarged prostate that affect the prostate can result in abnormal PSA levels, doctors can measure the level of PSA in the blood to diagnose and track prostate diseases.
Prostate Function
The prostate is a walnut-sized gland that consists of two lobes surrounded by an outer layer of tissue. Located in front of the rectum and below the bladder, the prostate encloses a portion of the urethra. This allows the prostate to perform its main function, which is to squeeze fluid into the urethra during sexual climax, but also means that the health of the prostate affects urinary function. The fluid produced by the prostate contains PSA and helps to nourish and protect the sperm.
Prostate Development
As a man ages, the prostate gland goes through two main phases of growth, as described by the National Kidney and Urologic Diseases Information Clearinghouse. The first occurs during puberty when the prostate doubles in size. The second phase begins around the age of 25 when the prostate slowly begins to grow again. As the prostate continues to grow, it produces more and more PSA.
Abnormal PSA Level
As men age, the level of PSA rises, making it difficult for doctors to assign a label of abnormal for a PSA test. In general, a PSA test result of four nanograms per milliliter of blood causes concern and leads to additional testing, according to MedLine Plus and the National Institutes of Health.
Prostate Cancer
Abnormal PSA levels may indicate the presence of prostate cancer. Prostate cancer occurs when the cells in the prostate gland grow abnormally and out of control, producing a mass, or tumor. Normally the prostate contains a layer of epithelial cells, which produce PSA, surrounded by a basal cell layer and a basement membrane. The formation of the tumor disrupts the basal layer and membrane, allowing PSA direct access to the blood, as described by a study published by Balk and associates in the 2003 issue of the "Journal of Clinical Oncology."
Enlarged Prostate
According to the National Kidney and Urologic Diseases Information Clearinghouse, as 90 percent of men in their seventies and eighties have an enlarged prostate, a condition known as benign prostate hyperplasia. Because an enlarged prostate can produce increased levels of PSA, an abnormal result in a PSA test does not necessarily mean the patient has cancer. Therefore an abnormal PSA result prompts doctors to perform further testing such as a prostate biopsy.
