It is a protein produced by the prostate. The vast majority is released into the ejaculate but tiny amounts are released into the blood stream and can be detected by a simple blood test. Abnormally high levels of PSA can be an indication of disease of the prostate. Common reasons for a high PSA level in the blood stream may include prostate cancer, large prostates, inflammation or infection of the prostate. Obviously the first concern is to exclude prostate cancer.