What is PSA (Prostate-Specific Antigen)?
PSA stands for prostate-specific antigen and is a protein (enzyme) produced by the prostate gland in men. PSA is normally secreted into the seminal fluid where it helps liquefy the gel-like substance that surrounds sperm after ejaculation, which is important for sperm motility.
A small amount of PSA also leaks from the prostate gland into the bloodstream, which is why PSA can be measured through a blood test. As a result, even completely healthy men have small amounts of PSA in their blood. PSA testing was introduced into clinical practice in the late 1980s and is today one of the most important laboratory tests used in the evaluation of prostate cancer.
What can cause elevated PSA levels?
PSA levels in the blood may increase in several conditions affecting the prostate gland. Prostate cancer is one possible cause, but an elevated PSA level does not automatically mean that cancer is present. There are several other common and often benign conditions that may lead to increased PSA levels.
Examples of conditions that may increase PSA include:
Examples of conditions that can raise PSA include:
- Benign enlarged prostate (benign prostatic hyperplasia, BPH).
- Inflammation of the prostate prostatitis.
- Urinary tract infection.
- Prostate cancer.
- Increased prostate volume with increasing age.
In prostate cancer, PSA levels may rise because the tumor disrupts prostate tissue, allowing more PSA to leak into the bloodstream. However, it is important to understand that benign conditions can also lead to clearly elevated PSA values.
PSA and age
PSA levels tend to increase with age because the prostate gland often enlarges as men grow older. For this reason, median PSA values are typically lower in younger men and higher in older men. This is why age-specific reference thresholds are used when evaluating PSA levels.
PSA threshold values
According to the Swedish National Guidelines for Prostate Cancer, the following PSA thresholds are commonly used as levels above which further medical evaluation may be recommended:
- 3 micrograms per liter (µg/L) for men under 70 years of age
- 5 micrograms per liter (µg/L) for men between 70 and 80 years of age
- 7 micrograms per liter (µg/L) for men over 80 years of age
If PSA levels exceed these thresholds, a physician may recommend further evaluation, for example consultation with a urologist or additional diagnostic investigations.
How is a PSA result interpreted?
A PSA result must always be interpreted in a clinical context. Physicians consider several factors when evaluating PSA levels, including the patient’s age, symptoms, previous PSA measurements, and risk factors such as a family history of prostate cancer.
In many cases, a mildly elevated PSA level may be rechecked after a period of time to evaluate whether the value remains stable or continues to increase. If prostate cancer is suspected, further evaluation may include a physical examination of the prostate, magnetic resonance imaging (MRI), or biopsy of prostate tissue.
Symptoms of prostate cancer
Prostate cancer often does not cause clear symptoms in its early stages. When symptoms occur, they may include one or more of the following:
- Increased frequency of urination
- Difficulty starting urination
- Weak urine stream
- Blood in the urine
These symptoms may also be caused by conditions other than prostate cancer, such as benign prostate enlargement, which is common in men over the age of 60. If prostate cancer has spread, additional symptoms may occur, including unexplained bone pain, fatigue, or loss of appetite.
PSA as a screening and health assessment tool
PSA testing is used both in medical evaluation and as part of health assessments to help detect potential signs of prostate cancer at an early stage. However, PSA testing has both benefits and limitations. Elevated PSA levels may lead to further diagnostic investigations in men who ultimately do not have cancer, while some prostate cancers may occur despite relatively low PSA levels.
For this reason, PSA results should always be interpreted together with other clinical information and, when appropriate, followed by additional diagnostic tests.
