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HCG human chorionic gonadotropin. By: Mr. Wael Laithi. 11/11/2013. HCG. Is a glycoprotein hormone produced during pregnancy that is made by the developing embryo after conception and later by the syncytiotrophoblast (part of the placenta)..
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HCG human chorionic gonadotropin By: Mr. WaelLaithi 11/11/2013
HCG • Is a glycoprotein hormone produced during pregnancy that is made by the developing embryo after conception and later by the syncytiotrophoblast (part of the placenta).. • Some cancerous tumors produce this hormone (germ cell tumors , gestational trophoblastic disease.) • Levels can first be detected by a blood test about 6-12 days after conception and Urine test about 12 - 14 days after conception. • In general the HCG levels will double every 72 hours. The level will reach its peak in the first 8 - 11 weeks of pregnancy and then will decline and level off for the remainder of the pregnancy.
HCG hormone maintains production of progesterone from the ovary, a crucial factor in maintaining a pregnancy. • Blood Test either Qualitative or Quantitative. • Blood pregnancy tests will yield a positive result if they detect 5 mIU/ml (milli-International Units per milliliter) of HCG in the blood.
Qualitative Blood Serum Test: • This test can only confirm whether or not the pregnancy hormone, hCG, is present and, therefore, whether a woman is pregnant or not. • The qualitative hCG blood test tends to be about as accurate as a home urine test.
Quantitative Blood Serum Test: • This test, also known as the beta hCG test, can measure the level of hCG in the blood. • Because it can detect even trace amounts of hCG, this is a very accurate test. • HCG levels generally double approximately every 2 days for the first four weeks of pregnancy. • A quantitative blood test can be helpful in confirming a pregnancy and can help assess whether or not a pregnancy is progressing normally.
Blood Test Results: • Blood tests have a 98-99% accuracy rate. • As with urine pregnancy tests, it is possible to end up with false results (both negative and positive) from a blood pregnancy test. • False negative results usually occur if the test was performed too early. This is because there may not be enough hCG in the blood to detect a pregnancy. • False positive results may appear if you are taking a medication that contains hCG.
Mechanism • Human chorionic gonadotropin interacts with the LHCG receptor and promotes the maintenance of the corpus luteum during the beginning of pregnancy, causing 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. • Due to its highly-negative charge, hCG may repel the immune cells of the mother, protecting the fetus during the first trimester.
It has also been suggested that hCG levels are linked to the severity of morning sickness in pregnant women. • Because of its similarity to LH, 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 pregnant women to extract hCG for use in fertility treatment.
Human chorionic gonadotropin also plays a role in cellular differentiation/proliferation and may activate apoptosis. • During first few months of pregnancy, the transmission of HIV-1 from woman to fetus is extremely rare. It has been suggested that this is due to the high concentration of hCG, and that the beta-subunit of this protein is active against HIV-1 • Because hCG is produced also by some kinds of tumor, hCG is an important tumor marker, but it is not known whether this production is a contributing cause or an effect of tumorigenesis.
Production • Like other gonadotropins, hCG can be extracted from urine or by genetic modification. • Pregnyl, Follutein, Profasi, and Novarel use the former method, derived from the urine of pregnant women. • Ovidrel, on the other hand, is a product of recombinant DNA.
Testing • Levels of hCG may be measured in the blood or urine. • Testing for hCG may also be done when diagnosing or monitoring germ cell tumors and gestational trophoblastic disease. • Most tests employ a monoclonal antibody, which is specific to the β-subunit of hCG (β-hCG). This procedure is employed to ensure that tests do not make false positives by confusing hCG with LH and FSH.
The urine test may be a chromatographic immunoassay , detection thresholds range from 20 to 100 mIU/ml. • Early in pregnancy, more accurate results may be obtained by using the first urine of the morning when hCG levels are highest. • When the urine is dilute (specific gravity less than 1.015), the hCG concentration may not be representative of the blood concentration, and the test may be falsely negative.
The serum test, using 2-4 mL of venous blood, is typically a chemiluminescent or fluorimetric immunoassay that can detect βhCG levels as low as 5 mIU/ml and allows quantification of the βhCG concentration. • The ability to quantitate the βhCG level is useful in the monitoring germ cell and trophoblastic tumors, • followupcare after miscarriage, and in diagnosis of and follow-up care after treatment of ectopic pregnancy. The lack of a visible fetus on vaginal ultrasound after the βhCG levels have reached 1500 IU/ml is strongly indicative of an ectopic pregnancy.
Gestational trophoblastic • A disease like Hydatidiform moles ("molar pregnancy") or Choriocarcinoma may produce high levels of βhCG (due to the presence of syncytialtrophoblasts- part of the villi that make up the placenta) despite the absence of an embryo. • This, as well as several other conditions, can lead to elevated hCG readings in the absence of pregnancy. • hCG levels are also a component of the triple test, a screening test for certain fetal chromosomal abnormalities/birth defects.
Reference levels: The following is a list of serum hCG levels. (LMP is the last menstrual period)
Tumor marker • The β subunit of human chorionic gonadotropin is secreted also by some cancers including choriocarcinoma, germ cell tumors, hydatidiform mole formation, teratoma with elements of choriocarcinoma (this is rare), and islet cell tumor. For this reason a positive result in males can be a test for testicular cancer.
Fertility • In the presence of one or more mature ovarian follicles, ovulation can be triggered by the administration of hCG. As ovulation will happen about 36–48 hours after the injection of hCG, procedures can be scheduled to take advantage of this time sequence. • Thus, patients that undergo IVF, in general, receive hCG to trigger the ovulation process, but have their eggs retrieved at about 36 hours after injection, a few hours before the eggs actually would be released from the ovary. • As hCG supports the corpus luteum, administration of hCG is used in certain circumstances to enhance the production of progesterone.
In the male, hCG injections are used to stimulate the leydig cells to synthesize testosterone. The intratesticular testosterone is necessary for spermatogenesis from the sertoli cells. Typical uses for hCG in men include hypogonadism and fertility treatment.
transvaginal ultrasound • A transvaginal ultrasound should be able to show at least a gestational sac once the hCG levels have reached between 1,000 - 2,000 mIU/ml. • Because levels can differentiate so much and conception dating can be wrong, a diagnosis should not be made by ultrasound findings until the hCG level has reached at least 2,000.
hCG levels after a pregnancy loss. • Most women can expect their levels to return to a non-pregnant range about 4 - 6 weeks after a pregnancy loss has occurred. • This can differentiate by how the loss occurred (spontaneous miscarriage, D&C procedure, abortion, natural delivery) and how high the levels were at the time of the loss. • Health care providers usually will continue to test hCG levels after a pregnancy loss to ensure they return back to <5.0
When to Order • A qualitative urine or blood hCG test is ordered as early as 10 days after a missed menstrual period when a woman wishes to confirm whether or not she is pregnant (some methods can detect hCG even earlier, at one week after conception). • Several quantitative blood hCG tests may be ordered over several days to rule out an ectopic pregnancy or to monitor a woman after a miscarriage. • A quantitative hCG test may also be ordered when a doctor suspects that a person may have gestational trophoblastic disease or a germ cell tumor. It may be ordered periodically to monitor the effectiveness of treatment and to detect tumor recurrence.
High Results of HCG? • In non-pregnant women, hCG levels are normally undetectable. • During early pregnancy, the hCG level in the blood doubles every two to three days. • Ectopic pregnancies usually have a longer doubling time. • Those with failing pregnancies will also frequently have a longer doubling time or may even show falling hCG concentrations.
hCG concentrations will drop rapidly following a miscarriage. • If hCG does not fall to undetectable levels, it may indicate remaining hCG-producing tissue that will need to be removed. • During treatment for gestational trophoblastic disease or a germ cell tumor, a falling hCG level generally indicates that the condition is responding to treatment, while rising levels may indicate that it is not responding to therapy. An increased hCG level after treatment may indicate a recurrence of disease.
False Results: • Tests performed too early in the pregnancy, before there is a significant hCG level, may give false-negative results, while blood or protein in the urine may cause false-positive results. • Urine hCG tests may give a false-negative result in very dilute urine. Women should not drink large amounts of fluid before collecting a urine sample for a pregnancy test. • Certain drugs such as diuretics and promethazine (an antihistamine) may also cause false-negative urine results.
Other drugs such as anti-convulsants, anti-parkinson drugs, hypnotics, and tranquilizers may cause false-positive results. • There are reports of false-positive serum hCG results due to several different compounds (not drugs) that may interfere with the test. These include certain types of antibodies that may be present in some individuals and fragments of the hCG molecule. • Generally, if results are questionable, they may be confirmed by testing with a different method.
