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Beta-subunit of human chorionic gonadotropin (beta-hCG)

Beta-subunit of human chorionic gonadotropin is one of the subunits of a specific hormone molecule - chorionic gonadotropin, which is formed in the shell of the human embryo. The analysis is carried out for the purpose of early diagnosis of pregnancy, detection of its complications and diagnosis of diseases associated with impaired hCG secretion.

Synonyms Russian

Beta subunit of hCG.

Synonyms English

Human Chorionic Gonadotropin, hCG, b-HCG, Quantitative hCG; Beta hCG, Total hCG, Total beta hCG.

Test method

Electrochemiluminescent immunoassay (ECLIA).

Detection range: 0.1 - 1,000,000 IU/L.

Units

IU/l (international unit per litre).

What biomaterial can be used for research?

Venous blood.

How to properly prepare for an examination?

• Do not smoke for 30 minutes before the test.

Study Overview

Human chorionic gonadotropin (hCG) is a hormone produced in the fetal membrane of the human embryo. It is an important indicator of the development of pregnancy and its deviations. It is produced by the cells of the chorion (the shell of the embryo) immediately after it is attached to the wall of the uterus (this happens only a few days after fertilization). The embryo at this stage of pregnancy is a microscopic vesicle filled with fluid, the walls of which are made up of rapidly multiplying cells. From one part of these cells, the unborn child (embryoblast) develops, while from the cells outside the embryo, a trophoblast is formed - that part of the fetal egg, with which it is attached to the wall of the uterus. Later, the chorion is formed from the trophoblast.

Chorion performs the function of nourishing the embryo, being an intermediary between the body of the mother and the child. In addition, it produces chorionic gonadotropin, which, on the one hand, affects the formation of the child, on the other hand, it specifically affects the mother's body, ensuring a successful pregnancy. The appearance of this hormone in the body of a future mother at the initial stage of pregnancy explains the importance of the test for early diagnosis of pregnancy.

Chorionic gonadotropin stimulates the secretory function of the corpus luteum of the ovaries, which should produce the hormone progesterone, which maintains the normal state of the inner lining of the uterine wall - the endometrium. The endometrium provides reliable attachment of the fetal egg to the mother's body and its nutrition with all the necessary substances.

Due to a sufficient amount of human chorionic gonadotropin, the corpus luteum, which normally exists for only about 2 weeks during each menstrual cycle, does not undergo resorption after successful conception and remains functionally active throughout the entire period of pregnancy. Moreover, it is in pregnant women under the influence of chorionic gonadotropin that it produces very large amounts of progesterone. In addition, CG stimulates the production of estrogens and weak androgens by ovarian cells and promotes the development of the functional activity of the chorion itself, and later the placenta, which is formed as a result of the maturation and growth of the chorionic tissue, improving its own nutrition and increasing the number of chorionic villi.

Thus, the role of human chorionic gonadotropin lies in the specific and multifaceted effect on the body of a woman and the fetus in order to ensure a successful pregnancy. Based on the analysis for chorionic gonadotropin, the presence of chorionic tissue in the woman's body is determined, and hence pregnancy.

According to its chemical structure, chorionic gonadotropin is a combination of protein and complex carbohydrates, consisting of two parts (subunits): alpha and beta. The alpha subunit of chorionic gonadotropin is completely identical to the alpha subunits of the luteinizing, follicle-stimulating and thyroid-stimulating hormones of the pituitary gland, which perform functions that are largely similar to the function of chorionic gonadotropin, but not during pregnancy. The beta subunit of chorionic gonadotropin is unique, which, on the one hand, determines the specificity of its action, and, on the other hand, allows it to be identified in biological media. In this regard, this test is called "beta-subunit of human chorionic gonadotropin (beta-hCG)".

Knowing the level of beta-hCG in the blood, it is possible to diagnose pregnancy already on the 6-8th day after conception (in the urine, the concentration of beta-hCG reaches the diagnostic level 1-2 days later). Normally, during pregnancy between the 2nd and 5th weeks, the amount of beta-hCG doubles every 1.5 days. With multiple pregnancy, it increases in proportion to the number of fetuses. The maximum level of hCG reaches the 10-11th week, and then gradually decreases. This is due to the fact that from the beginning of the 2nd third of pregnancy, the placenta is able to independently produce enough estrogens and progesterone, with the participation of which the endometrium functions normally, regardless of the secretion of hormones in the ovarian corpus luteum. At the same time, the concentration of CG in the blood of a pregnant woman gradually decreases, and the corpus luteum can function without the effects of CG. During this period, the role of the hormone is to stimulate the production of testosterone in the fetus, which is necessary for the normal development of the external genital organs of the embryo.

Thus, during pregnancy, the level of beta-hCG in the blood first increases and then decreases. According to this indicator, one can judge the successful course of pregnancy and identify violations of the development of the fetus. The test for hCG in the blood is the most reliable method for determining pregnancy in the early stages. HCG appears in the body of a woman from 6-8 days after fertilization. A common rapid pregnancy test that every woman can use at home is also based on measuring hCG in the urine.

Below normal hormone levels at various stages of fetal development suggest ectopic pregnancy, fetal growth retardation, threatened miscarriage, non-progressive pregnancy, or placental insufficiency. The reason for the increased content of beta-hCG may be toxicosis, diabetes mellitus, or an incorrectly set gestational age. A high level of the hormone after a mini-abortion indicates a progressing pregnancy.

Determining the level of hCG is included in the triple test study, the results of which can be used to judge some anomalies in the development of the fetus, but an accurate diagnosis cannot be made. The study only allows you to classify a woman as a risk group for this pathology. In this case, further investigation is necessary. In non-pregnant women, CG is normally absent, but it can be secreted by some abnormal chorion-derived tissues (hydatidiform mole, chorionepithelioma) and some other tumors.

What is research used for?

• For the diagnosis of pregnancy, including multiple, ectopic and non-developing.
• To monitor the progress of pregnancy.
• To detect fetal growth retardation, threatened miscarriage, placental insufficiency.
• For the diagnosis of amenorrhea.
• To monitor the effectiveness of induced abortion.
• As part of a comprehensive examination to identify fetal malformations.
• For the diagnosis of CG-producing tumors.

When is the test ordered?

• If pregnancy is suspected, in particular multiple pregnancy.
• When monitoring the progress of pregnancy.
• When there is an assumption about a complication during pregnancy: fetal growth retardation, the threat of spontaneous abortion, non-developing or ectopic pregnancy, chronic placental insufficiency.
• Confirm successful induced abortion if necessary.
• With a comprehensive examination to identify fetal malformations.
• When finding out the reason for the absence of menstruation (amenorrhea).
• When is the diagnosis of tumors producing hCG.

What do the results mean?

Reference values ​​

Causes of high beta-hCG levels

In the absence of pregnancy, the result of the beta-hCG test should be negative. The detection of beta-hCG suggests that at least 5-6 days have passed since fertilization. Between the 2nd and 5th weeks of pregnancy, during its normal course, the level of beta-hCG doubles every 1.5 days and soon reaches its maximum. Then it starts to slowly decline. The results of the analysis are compared with the normal values ​​for each gestational age. For a correct interpretation of the results, it is necessary to know exactly when the conception occurred.

In pregnant women:

• multiple pregnancies (the rate increases in proportion to the number of fetuses),
• toxicosis,
• prolonged pregnancy,
• maternal diabetes mellitus,
• fetal malformations,
• taking synthetic hormones.

Not pregnant:

• hCG-producing tumors,
• surgical abortion (first 4-5 days after the procedure),
• taking hCG preparations.

Causes of low beta-hCG levels (during pregnancy):

• ectopic or non-developing pregnancy,
• fetal growth retardation,
• threatened miscarriage,
• chronic placental insufficiency,
• fetal death (in the 2nd-3rd trimester of pregnancy).

What can influence the result?

• When diagnosing pregnancy, taking the test too early - when less than 5 days have passed since conception - can lead to a false negative result.

Also recommended

• Alpha-fetoprotein (alpha-FP)
• Antiphospholipid antibodies IgG
• Antiphospholipid antibodies IgM
• Placental lactogen
• Free estriol
• Pregnancy - Prenatal screening for trisomies of the first trimester of pregnancy (Down syndrome), PRISCA
• Plasma pregnancy-associated protein A (PAPP-A)
• Pregnancy - Prenatal screening for trisomies of the second trimester of pregnancy, PRISCA
• Antibodies to steroid-producing cells of the placenta

Who orders the examination?

General practitioner, obstetrician-gynecologist, oncologist.

Literature

• Handbook of Clinical Laboratory Testing During Pregnancy, edited by Ann M. Gronowski. Springer-Verlag LLC, New York, 2004
• Prenatal Diagnosis in Obstetric Practice. M. J. J. Whittle, Blackwell Publishers 1995
• Endocrinology of Pregnancy. Fuller W. Bazer, Humana Press 1998
• Blood Biochemistry. N J Russell, G M Powell, J G Jones, P J, Winterburn and J M Basford, Croom Helm, London and Canberra, 1982
• Blood Chemistry and CBC analysis-Clinical Laboratory Testing from a Functional Perspective. Rychard Weatherby N.D and Scott Fergusson, N.D., Bear Mounting Publishing, 2002.
• Tietz Clinical Guide to Laboratory Tests. Alan H. B. Wu, Saunders/Elsevier, 2006
• Laboratory and Diagnostic Tests. Joyce LeFever Kee - Pearson, Prentice Hall, 8th Edition 2010
• District Laboratory Practice in Tropical Countries. Monica Cheesbrough, Cambridge University Press, second edition, 2005.
• Clinical Chemistry. A Laboratory Perspective. Wendy L. Arneson, Jean M. Brickell, F.A. Davis Company, 2007
• Clinical Chemistry. Michael L. Bishop, Edward P. Fody, Larry E. Schoef, Lippincott Williams & Wilkins, 2005

HCG test - Donate blood for pregnancy in Moscow (Human Chorionic Gonadotropin)

Beta hCG (Human Chorionic Gonadotropin) is a subunit of a specific hormone molecule that is formed in the shell of the human embryo. Determining the level of total beta-hCG is necessary for diagnosing pregnancy, monitoring its course, and this hormone also serves as a marker for certain oncological diseases.

Why is it important to test hCG during pregnancy

HCG begins to be produced in the chorion of the embryo shortly after implantation of the embryo. Already on the 6th day, its level becomes sufficient for testing in the blood, later, on average for a week, in the urine. That is, after a few days from the moment of the delay of menstruation, according to the indicators of this hormone, pregnancy is diagnosed. By the 7-11th week, the production of chorionic gonadotropin increases many times, then gradually decreases. For each period of bearing a child, there are hCG norms. Normal values ​​of the hormone indicate the successful course of pregnancy processes, deviations indicate the presence of pathologies.

"HCG norms by weeks of pregnancy"

“HCG norms by days of pregnancy”

The effect of human chorionic gonadotropin on the course of pregnancy

HCG has a direct effect on the suppression of the menstrual cycle and the maintenance of pregnancy. Thanks to hCG, the corpus luteum in the ovary does not dissolve, but continues to produce until the 12th week, while the placenta builds up, estrogens and progesterone, which prevents uterine contractions and reduces its tone. Chorionic gonadotropin also has a beneficial effect on the development and functioning of the placenta. In addition to acting on the ovaries, gonadotropin stimulates temporary hyperfunction of the adrenal cortex of a pregnant woman. Increased secretion of glucocorticoids helps to reduce the level of stress, including that caused by the immune response to the growth of the embryo, and increase the adaptive properties of the woman's body.

If there is a threat or presence of disorders during pregnancy, hCG analysis is carried out in dynamics by weeks. The assessment of the deviation of indicators from normal values ​​is carried out in conjunction with other studies, ultrasound data.

Pathologies can be the reason for the decrease in hCG:

• non-developing pregnancy;
• ectopic pregnancy;
• fetal developmental delay;
• threatened miscarriage, spontaneous abortion;
• insufficiency of functioning or aging of the placenta.

An excess of CG from normal values ​​is often not a sign of pathology, but requires a more thorough examination of the body of a pregnant woman, clarification of the gestation period.

The level of human chorionic gonadotropin increases in the following conditions:

• early and late toxicosis, in particular preeclampsia;
• multiple pregnancy;
• prediabetic;
• abnormalities in fetal chromosomes;
• the use of gestagens of synthetic origin.

The content of chorionic gonadotropin in the blood increases many times over normal values ​​for pregnancy in case of a serious pathology - hydatidiform mole. In this disease, the chorionic villi are converted into blisters filled with fluid. The tissues of the hydatidiform mole produce hCG intensively, which provokes the appearance of cysts in the ovaries. In some cases, up to 20% of the total, the drift degenerates into a malignant neoplasm, chorionepithelioma.

HCG test in the diagnosis of pathologies in non-pregnant women

A small amount of human chorionic gonadotropin is produced by the pituitary gland of healthy people, both men and women. Normally, its indicators in non-pregnant women are close to zero. An increase in CG outside of pregnancy occurs when hormonally active tumors form in the body, with the following pathologies:

• tapeworm infestations;
• choriocarcinoma;
• malignant neoplasms of the kidneys, gastrointestinal tract, lungs, uterus in women, testicles in men.

General recommendations

The level of human chorionic gonadotropin is determined in blood serum. Biomaterial is taken from a vein on an empty stomach. To obtain accurate results of the analysis, it is necessary to follow the recommendations:

1. Eating should be excluded for 4 hours.
2. In the days preceding the analysis, refrain from physical activity, sexual intercourse.

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