Prostate specific antigen

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

Biochemically it is a serine protease(EC3.4.21.77) enzyme, the geneof which is located on the nineteenth chromosome(19q13).

Higher than normal levels of PSA are associated with both localized and metastatic prostate cancer(PCa). PSA is normally present in the bloodat very low levels. Increased levels of PSA may 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 exametc. Recent research suggests that the rate of increase of PSA (the "PSA velocity") may be a more specific marker for prostate cancer.

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 ultrasoundimaging 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^{[{{fullurl:Template:FULLPAGENAME}}#endnote_1]}.

The currentguidelines of the American Cancer Societyrecommend 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..."

Reference

• ^  Thompson IM, Pauler DK, Goodman PJ, Tangen CM, Lucia MS, Parnes HL, Minasian LM, Ford LG, Lippman SM, Crawford ED, Crowley JJ, Coltman CA Jr. Prevalence of prostate cancer among men with a prostate-specific antigen level < or =4.0 ng per milliliter. N Engl J Med2004;350:2239-46. PMID 15163773.

External link

• PSA resourcees:antígeno prostático específico

fr:Antigène prostatique spécifique ja:???????(PSA) pl:PSA (antygen)

This article is licensed under the GNU Free Documentation License.
It uses material from the http://en.wikipedia.org/wiki/Prostate+specific+antigen Wikipedia article Prostate specific antigen.