Prostate specific antigen

Prostate specific antigen (PSA, also known as kallikrein III, seminin, semenogelase, γ-seminoprotein and P-30 antigen) is a protein manufactured almost exclusively by the prostate gland; PSA is produced for the ejaculate where it liquifies the semen and allows sperm to "swim" freely. It is also believed to be instrumental in dissolving the cervical mucous cap, allowing the entry of sperm.

Related Topics:
Protein - Sperm

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Biochemically it is a serine protease ({{EC number|3.4.21.77}}) enzyme, the gene of which is located on the nineteenth chromosome (19q13).

Related Topics:
Serine protease - Enzyme - Gene - Chromosome

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High levels of PSA are associated with benign prostatic hyperplasia and prostate cancer. PSA is normally present in the blood at very low levels. Increased levels of PSA suggest the presence of prostate cancer. However, prostate cancer can also be present in the complete absence of an elevated PSA level. PSA levels can be also elevated due to prostate infection, irritation, benign prostatic hypertrophy (enlargement) or hyperplasia (BPH), recent ejaculation, digital rectal exam etc.

Related Topics:
Benign prostatic hyperplasia - Prostate cancer - Blood - Digital rectal exam

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The U.S. Food and Drug Administration (FDA) has approved the PSA test for annual screening of prostate cancer in men of age 50 and older. PSA levels between 4 and 10 ng/mL (nanograms per milliliter) are considered to be suspicious and should be followed by rectal ultrasound imaging and, if indicated, biopsy. PSA is false positive-prone: 7 out of 10 men in this category will still not have prostate cancer, and false-negative-prone: 2.5 out of 10 men with no elevation in PSA will have prostate cancer{{ref|1}}.

Related Topics:
Ultrasound - Biopsy - False positive

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The current guidelines of the American Cancer Society recommend that non-African American men over age 50 should be "offered" a prostate exam every year. African-American men and those with a family history of prostate cancer should be screened annually upon reaching 40 years. These guidelines may be changing. A new European study has shown that a thorough screening for prostate cancer every 4 years is adequate. The screening comprises a PSA blood test, a digital rectal exam, and a transrectal ultrasound. "Very few, if any, aggressive prostate cancers escape (this) screening..."

Related Topics:
Current - American Cancer Society

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