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Chorionic gonadotropin

Human chorionic gonadotropin (hCG) is a peptide hormone produced in pregnancy, that is made by the embryo soon after conception and later by the trophoblast (part of the placenta). Its role is to prevent the disintegration of the corpus luteum of the ovary and thereby maintain progesterone production that is critical for a pregnancy in humans. hCG may have additional functions, for instance it is thought that it affects the immune tolerance of the pregnancy. Early pregnancy testing generally is based on the detection or measurement of hCG. more...

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The drugs Pregnyl®, Follutein®, and Ovidrel® use chorionic gonadoptropin as the active ingredient in their product. These preparations are used in assisted conception in lieu of luteinizing hormone to trigger ovulation.

Structure

hCG is a glycoprotein composed of 237 amino acids with a molecular mass of 36.7 kDa. It is heterodimeric, with an α (alpha) subunit identical to that of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and thyroid-stimulating hormone (TSH). Its β (beta) subunit is unique to hCG.

Function

hCG promotes the maintenance of the corpus luteum and causes it to secrete the hormone progesterone. Progesterone enriches the uterus with a thick lining of blood vessels and capillaries so that it can sustain the growing fetus.

Because of its similarity to LH and FSH, hCG can also be used clinically to induce ovulation in the ovaries as well as testosterone production in the testes. As the most abundant biological source is women who are presently pregnant, some organizations collect urine from gravidae to extract hCG for use in fertility treatment.

Pregnancy testing

Pregnancy tests measure the levels of hCG in the blood or urine to indicate the presence or absence of a fertilized egg. In particular, most pregnancy tests employ an antibody that is specific to the β-subunit of hCG (βhCG). This is important so that tests do not make false positives by confusing hCG with LH and FSH. (The latter two are always present at varying levels in the body, while hCG levels are negligible except during pregnancy.) The urine test is a chromatographic immunoassay that can detect levels of βhCG as low as 25-100 mIU/ml. The urine should be the first urine of the morning when hCG levels are highest. If the specific gravity of the urine is above 1.015, the urine should be diluted. The serum test, using 2-4 mL of venous blood, is a radioimmunoassay (RIA) that can detect βhCG levels as low as 5 mIU/ml and allows quantitation of the βhCG concentration. The ability to quantitate the βhCG level is useful in the evaluation of ectopic pregnancy and in monitoring germ cell and trophoblastic tumors.

Hydatiform moles ("molar pregnancy") may produce high levels of βhCG, despite the absence of an embryo. This can lead to false positive readings of pregnancy tests.

Tumor marker

βhCG is also secreted by some cancers including teratomas, choriocarcinomas and islet cell tumors. When a patient is suspected of harboring a teratoma (often found in the testes and ovaries but also in the brain as a dysgerminoma), a physician may consider measuring βhCG. Elevated levels cannot prove the presence of a tumor, and low levels do not rule it out (an exception is in males who do not naturally produce βhCG). Nevertheless, elevated βhCG levels fall after successful treatment (e.g. surgical intervention or chemotherapy), and a recurrence can often be detected by the finding of rising levels.

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Human chorionic gonadotropin pregnancy test
The most common test of pregnancy involves the detection of a hormone known as human chorionic gonadotropin (hCG) in a sample of blood or urine.
A Comparison of Human Chorionic Gonadotropin-Related Components in Fresh Frozen Serum With the Proficiency Testing Material Used by the College of American
Context.-As part of a College of American Pathologists (CAP) proficiency testing survey, a comparison is made between human chorionic gonadotropin (hCG) ...
Comparison of Fresh Frozen Serum to Proficiency Testing Material in College of American Pathologists Surveys: [alpha]-Fetoprotein, Carcinoembryonic Antigen,
Context.-Most proficiency testing materials (PTM) contain an artificial matrix that may cause immunoassays to perform differently with this material than ...
Chorionic villus sampling
Chorionic villus sampling (CVS), also known as chorionic villus biopsy, is a prenatal test that can detect genetic and chromosomal abnormalities of an unborn baby.
The Pregnancy That Never Was—Beta Human Chorionic Gonadotropin Secreting Primary Lung Cancer - Abstract
Jennifer Anne LaRosa, MD; TB Pustilnik, MD; PJ O'Reilly, MD; MR Waldrum, MD; SM Harding, MD; MF Carcelen, MD--The University of Alabama at Birmingham, ...
Pregnancy
The period from conception to birth. After the egg is fertilized by a sperm and then implanted in the lining of the uterus, it develops into the placenta ...
Testicular cancer
Testicular cancer is a cancerous growth occurring in the male gonads, or testes. The testes are located outside the body cavity, in the scrotum.
Hydatidiform mole
A hydatidiform mole is a relatively rare condition in which tissue around a fertilized egg that normally would have developed into the placenta instead ...

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