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What is Intact Human Chorionic Gonadotropin?

Medically Reviewed by Dan Brennan, MD on June 17, 2021

Intact human chorionic gonadotropin is a variant of human chorionic gonadotropin hormone.

This helps tissue grow and form correctly during pregnancy.

What is human chorionic gonadotropin?

Human chorionic gonadotropin comes from trophoblastic tissue. Trophoblastic tissue is a tissue that develops in the baby during the early days of pregnancy. It later forms part of the placenta. The primary function of human chorionic gonadotropin is to help support your pregnancy. It does so by stimulating the corpus luteum (the follicle that houses a maturing egg) to make the hormone progesterone which keeps your pregnancy going.

It is a form of human chorionic gonadotropin that's active biologically. ‌

Human chorionic gonadotropin is also made by your liver, pituitary gland, and colon.

The hormone is made of two subunits:

  1. Alpha subunit
  2. Beta subunit

Human chorionic gonadotropin also exists in other different variants in your urine and blood:

  • Nicked human chorionic gonadotropin
  • Nicked free beta subunit
  • Free beta subunit
  • Beta-core fragment (found in urine)‌

You may use traces of human chorionic gonadotropin in the urine to find out if you are pregnant. You can measure human chorionic gonadotropin levels to help you find out whether you are carrying a viable or an ectopic pregnancy.

An ectopic pregnancy is when there's a pregnancy outside of your uterus, where a baby normally grows.

Apart from pregnancy, other issues could be causing the production of human chorionic gonadotropin. Cancers are a known cause of high human chorionic gonadotropin levels in serum (the liquid part of your blood).

The Roles of Intact Human Chorionic Gonadotropin

Intact human chorionic gonadotropin performs several roles in your body:

  • It prolongs the lifespan of the corpus luteum.
  • It becomes thyrotropic (stimulates the thyroid gland) when at a high concentration.
  • It helps keep the level of progesterone high during the early days of pregnancy.‌

Its role in screening Down's syndrome: Intact human chorionic gonadotropin increases chances of detecting Down's syndrome as early as the second trimester. It has higher accuracy than free beta-human chorionic gonadotropin subunits (which can also identify the condition in developing babies).

Also, using intact human chorionic gonadotropin reduces the risk of false-positive results.

How to Detect Intact Human Chorionic Gonadotropin

The following tests can detect intact human chorionic gonadotropin:‌

  1. Serum testing. Human chorionic gonadotropin can be found in serum (the liquid part of your blood). This test must be carried out in a lab. With the serum test, it is possible to do both quantitative and qualitative measurements. 
  2. Urine testing. Urine tests are most common with pregnancy testing. The test is quite accurate in detecting pregnancies. However, you can only do qualitative testing. Quantitative testing of human chorionic gonadotropin is impossible with a urine sample. That means that the test can only show human chorionic gonadotropin is present, not the specific levels.

It is common to get false negative or positive human chorionic gonadotropin test results.

Potential factors that may interfere with these results include:

  • Drugs or medication use
  • Human error while interpreting results
  • Blood or protein in the urine
  • Diluted urine 
  • Taking measurement too early in the pregnancy

Uses of HCG Tests

Human chorionic gonadotropin tests are used to:

  • Detect pregnancy. Testing human chorionic gonadotropin levels together with a good history and physical examination is an accurate way of finding out if you are pregnant. Human chorionic gonadotropin is detectable in urine one or two days after conception. In serum, the hormone may be seen after nine to 10 days. Human chorionic gonadotropin tests are FDA-approved to test for pregnancy. 
  • Detect some cancers. Human chorionic gonadotropin assays help find out the possibility of gestational trophoblastic disease. The presence of human chorionic gonadotropin without pregnancy is a common sign of cancer. Due to this, human chorionic gonadotropin is used as a tumor marker. Some common examples of cancers that produce human chorionic gonadotropin include lung cancer, breast cancer, ovarian cancer, gastrointestinal (GI) cancers, melanomas, and more.
  • Screening for Down syndrome. Measuring human chorionic gonadotropin levels during the first and second trimesters may help detect down syndrome.
  • Diagnose ectopic pregnancy. An ectopic pregnancy is diagnosed after taking a series of human chorionic gonadotropin tests and careful observation of symptoms that are common with the condition.‌

Human chorionic gonadotropin levels in your serum increase two times every two days of the first trimester in a normal pregnancy. If it takes longer for the human chorionic gonadotropin concentration to double, this may show you have an ectopic pregnancy. A serum human chorionic gonadotropin test may be used to find out if you have an ectopic pregnancy.

WebMD Medical Reference

Sources

SOURCES:

‌American Association for Clinical Chemistry: "Human Chorionic Gonadotropin."

‌Betz, D., Fane, K. Human Chorionic Gonadotropin, StatPearls Publishing, 2020.

Encyclopaedia Britannica: "Corpus luteum."

Merriam-Webster: "thyrotropic."

Obstetrics & Gynecology: "Free beta-hCG subunit versus intact hCG in Down syndrome screening."

University of Utah School of Medicine: "The Analytical & Clinical Complexities of Human Chorionic Gonadotropin Tests."

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