Prostate-Specific Antigen (PSA) testing is a common screening tool, but an elevated result often causes concern. The most frequent cause of a high PSA is not cancer, but a benign condition known as Benign Prostatic Hyperplasia (BPH), or an enlarged prostate. The relationship between these two factors is frequently misunderstood, creating a diagnostic challenge for physicians and confusion for men undergoing screening. This article explores how prostate enlargement affects PSA levels and how doctors differentiate this elevation from a potentially cancerous one.
Understanding PSA and Prostate Enlargement
The prostate is a small gland beneath the bladder responsible for producing seminal fluid. As men age, the prostate often grows larger, a non-cancerous condition called Benign Prostatic Hyperplasia (BPH). BPH is common, affecting nearly 90% of men over 80, and the enlargement can press on the urethra, causing urinary symptoms like a frequent or weak stream.
PSA is a protein produced exclusively by prostate cells, functioning to liquefy semen after ejaculation. A small amount naturally leaks into the bloodstream, which the PSA blood test measures. The test is sensitive enough to detect any increase in the total amount of prostate tissue.
The Direct Link How BPH Affects PSA Levels
An enlarged prostate directly increases the PSA level because a larger gland contains more tissue and, therefore, more PSA-producing cells. Benign prostate tissue actively produces PSA, and as the gland grows, the volume of the protein released into the blood rises proportionally. This relationship between prostate size and PSA is a reason why BPH causes elevated results.
The physical enlargement of the prostate can also contribute to a higher PSA through a mechanical effect. The sheer volume of the enlarged tissue places pressure on the gland’s internal architecture, which can cause a minor disruption of the delicate blood vessels. This pressure facilitates the leakage of PSA protein into the bloodstream, further elevating the measured level. Inflammation of the prostate (prostatitis) frequently occurs alongside BPH and can cause a temporary rise in PSA levels.
Differentiating High PSA BPH Versus Prostate Cancer
PSA is considered a biomarker that is sensitive to prostate changes but lacks specificity, meaning it rises due to BPH, infection, or cancer. For men with PSA results in the “gray zone” (typically between 4.0 and 10.0 nanograms per milliliter, or ng/mL), doctors use specialized metrics to determine the likelihood of cancer versus BPH.
PSA Density (PSAD)
PSAD is calculated by dividing the total PSA level by the volume of the prostate gland, often measured by transrectal ultrasound. A PSAD greater than 0.15 ng/mL per cubic centimeter suggests a higher risk of cancer. This indicates a high concentration of PSA within a smaller gland, which is less common in BPH.
Free-to-Total PSA Ratio
This ratio measures the percentage of PSA in the blood that is not bound to other proteins. In men with BPH, a larger proportion of the protein remains unbound, or “free.” A ratio above 25% often suggests benign enlargement. Conversely, cancer cells produce more bound PSA, so a lower ratio, particularly below 10%, raises suspicion for malignancy.
PSA Velocity
PSA Velocity measures the rate at which the PSA level increases over time. A slow, gradual increase is consistent with the slow growth of BPH tissue. However, a rapid rise, such as an increase of 0.75 ng/mL or more per year, warrants further investigation for cancer.
Next Steps After a High PSA Result
When an initial PSA test is high, the first step is often to repeat the test after four to six weeks to rule out temporary causes like recent ejaculation or infection. If the repeated test remains elevated, the physician typically performs a digital rectal examination (DRE) to feel for abnormal firmness or nodules. If infection (prostatitis) is suspected, a course of antibiotics may be prescribed before retesting the PSA.
If specialized PSA metrics and the DRE suggest elevated risk, advanced imaging is the next step. A multi-parametric Magnetic Resonance Imaging (mpMRI) scan is used to identify suspicious lesions that could indicate cancer. This imaging helps guide the decision for a biopsy and assists in targeting concerning areas during the procedure. A prostate biopsy is the only way to definitively diagnose cancer and is recommended when risk factors, including PSA metrics and MRI findings, cross a certain threshold.