Table of Contents
Definition of Prostate-specific Antigen (PSA)
An enzyme prostate gland cells produce. Prostatic fluid, the cumulative secretions of prostate gland cells, contains high levels of PSA. PSA acts on the jellylike substance that encases sperm during their storage in the seminal vesicles, liquefying the substance when the sperm mix with prostatic fluid in the urethra during ejaculation. This action restores motility to the sperm.
Measuring the blood concentration of PSA provides information about the health status of the prostate gland. In the healthy prostate gland of a man under age 40, the prostate gland cells form a tight structure that directs nearly all PSA the cells produce into the prostatic fluid; only a small amount of PSA escapes to circulate in the blood.
In certain health conditions, most notably prostate cancer, PSA blood levels rise. Prostate cancer disrupts the structure and organization of prostate gland cells, allowing much higher concentrations of PSA to enter the blood circulation.
As well, PSA also normally rises with increasing age because the prostate gland slowly enlarges beginning around age 40, a process that also alters the structure and organization of prostate gland cells. Because of this natural change, normal PSA blood values differ according to a man’s age.
Blood PSA concentrations above the value for age may suggest the presence of prostate disease, including prostate cancer. In general, a blood PSA level of 4 nanograms per milliliter (ng/mL) may indicate the need for further evaluation of the prostate gland’s health.
|NORMAL VALUES FOR BLOOD PROSTATE-SPECIFIC ANTIGEN (PSA) LEVELS|
|Age||PSA Blood Concentration|
|40 to 49||< 2.5 nanograms per milliliter (ng/mL)|
|50 to 59||< 3.5 ng/mL|
|60 to 69||< 4.5 ng/mL|
|70 to 79||< 6.5 ng/mL|
However, health experts disagree about the value of blood PSA levels for prostate cancer screening and detection. There is limited consensus around what the values mean, there are several methods for measuring PSA that are not equivalent to one another, and there is a higher rate of false-positive PSA results—PSA levels that are elevated for reasons other than prostate disease-than many doctors find acceptable.
These factors are of concern because the next step of diagnosis, biopsy, is invasive and carries risk for numerous complications. Many doctors find PSA blood tests more useful when treating disorders of the prostate gland, such as BPH and prostate cancer, as measures to help assess the effectiveness of treatment.
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