KLK3, more widely recognized as Prostate-Specific Antigen (PSA), is an important protein in male health. Its detection in blood has influenced how prostate conditions are approached and managed. As a biomarker, PSA provides insights into the state of the prostate gland, particularly concerning the possibility of disease.
What is KLK3 (Prostate-Specific Antigen)?
KLK3, or Prostate-Specific Antigen (PSA), is a protein belonging to the kallikrein family. This enzyme is predominantly produced by the epithelial cells within the prostate gland, a small organ located beneath the bladder in males.
The normal biological function of KLK3 involves the liquefaction of seminal coagulum after ejaculation. It achieves this by breaking down high molecular weight proteins, such as semenogelin-1, into smaller peptides, which allows for increased sperm motility. In healthy individuals, only a small amount of this protein enters the bloodstream.
KLK3’s Role in Prostate Health
PSA serves as a biomarker in assessing prostate health and is used clinically. Its primary application is screening for prostate cancer, identifying individuals who may require further evaluation, such as a biopsy. Elevated levels can prompt a physician to investigate the prostate more thoroughly.
Beyond initial screening, PSA testing assists in diagnosing prostate conditions by guiding decisions about prostate biopsies. It also monitors the effectiveness of treatments for prostate cancer; a decline in PSA levels after therapy can indicate a positive response, while a rise may signal recurrence. While PSA is associated with prostate cancer, elevated levels can also indicate other non-cancerous conditions, such as benign prostatic hyperplasia (BPH), which is an enlargement of the prostate, or prostatitis, an inflammation of the prostate gland.
Interpreting KLK3 Test Results
Interpreting PSA test results requires understanding that “normal” ranges can vary, considered to be below 4.0 nanograms per milliliter (ng/mL) for many men, though this can differ based on age and other factors. A higher PSA level does not automatically mean prostate cancer is present, as various factors can influence these levels. For instance, age can impact PSA, with levels increasing as men get older.
The size of the prostate gland can also affect PSA readings, as larger glands produce more PSA. Recent activities like ejaculation or a digital rectal examination (DRE) can temporarily elevate PSA levels. Certain medications and conditions like prostate inflammation (prostatitis) can also lead to increased PSA. Healthcare providers consider all these variables when evaluating a patient’s PSA result to determine the most appropriate next steps.
Nuances and Limitations of KLK3 Testing
Despite its utility, PSA testing presents complexities and limitations. A concern is false positives, where elevated PSA levels are detected but no cancer is found after further investigation. This can lead to unnecessary anxiety and medical procedures like biopsies, which carry risks. Conversely, false negatives can occur, meaning PSA levels appear normal even when prostate cancer is present.
PSA testing also carries risks of overdiagnosis and overtreatment. This involves detecting and treating slow-growing prostate cancers that might never have caused symptoms or threatened life. Treatments can lead to side effects like incontinence or erectile dysfunction, impacting quality of life without a clear survival benefit. Medical guidelines emphasize shared decision-making, where patients and providers discuss the potential benefits and harms of PSA testing.