What does hCG means?
In molecular biology, human chorionic gonadotropin (hCG) is a hormone produced by the the fertilized egg within the syncytiotrophoblast which later develops to the placenta.
In biochemistry: HCG is shortcut to Human chorionic gonadotropiand n is a glycoprotein composed of 237 amino acids with a molecular mass of 25.7 kDa
The alpha subunit is the same one used by other sex/pituitary hormones: FSH, LH, and TSH. The beta subunit, though, is unique to HCG and that’s why pregnancy tests look for the presence of beta-HCG.
LH hormone produced in the pituitary gland of males and females of all ages and resemble HCG in its structure.
What does β beta subunit means?
HCG hormone is heterodimeric protein, with an α (alpha) subunit identical to that of luteinizing hormone (LH), follicle-stimulating hormone (FSH), thyroid-stimulating hormone (TSH), and β (beta) subunit that is unique to hCG.
Learn when to take pregnancy test?
What is the blood tests measure hcg beta subunit levels?
In the medical Lab ask for a test called one of these:
Measurement of serum total human chorionic gonadotrophin
Measurement of serum total human chorionic gonadotropin
Serum total HCG level
Serum total HCG measurement
Serum total human chorionic gonadotrophin measurement
Serum total human chorionic gonadotropin measurement
What does the hcg hormone do?
- BHCG promotes the maintenance of the corpus luteum during the beginning of pregnancy. This allows the corpus luteum to secrete the hormone progesterone during the first trimester by interactaction with the LHCG receptor of the blastocyst.
- Progesterone enriches the uterus with a thick lining of blood vessels and capillaries so that it can sustain the growing fetus.
- HCG hormone protecting the fetus during the first trimester from the immune cells of the mother because the BHCG horomone has a strong negative charge.
- Human chorionic gonadotropin “BHCG “ also plays a role in cellular differentiation/proliferation and may activate apoptosis.
- Not proven jobs of B-hCG: HCG may be a placental link for the development of local maternal immunotolerance, the matter will lead to expedite fetal development in the endometrium.HCG levels are linked to the severity of morning sickness in pregnant women.
Is urine pregnancy test is accurate or the blood test?
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.
Best and accurate methods to test for beta subunit hCG level:
B-HCG detected in Blood or urine samples for qualitative measurement of hCG. hCG levels are also a component of the triple test, a screening test for certain fetal chromosomal abnormalities/birth defects.
Triple test contains these tests: Alpha-fetoprotein radioimmunoassay, Chorionic gonadotropin beta-subunit measurement, Estradiol measurement, and Serum progesterone measurement
Chemical assays can detect “all known forms of hCG and its break down products present in serum and urine samples in pregnancy, cancer and trophoblastic disease: regular hCG, nicked hCG, hyperglycosylated hCG, hCG missing the ß-subunit C-terminal peptide, free ß-subunit, nicked free ß-subunit, free ß-subunit missing the CTP, and urine ß-core fragment.” All of these are variations/mutations in HCG.
Urine Pregnancy test:
The most sensitive urine tests usually detect hCG between 6 and 12 days post ovulation.
Pregnancy urine dipstick tests are based on the lateral flow technique depending on the brand of test, the detection thresholds range from 20 to 100 mIU/ml, also urine tests may be found as chromatographic immunoassay methods or other test formats, home baby check tests, physician’s office pregnancy tests, or laboratory-based rapid tests.
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.
Blood pregnancy tests:
By drawing a blood sample usually 2-4 mL of venous blood and test serum for b-hCG level.
Blood quantitive test for beta-subunit hCG use techniques called a chemiluminescent or fluorimetric immunoassay technqiues that can detect βhCG levels as low as 5 mIU/ml and allows high accurate quantification of the βhCG concentration.
Many hCG immunoassays are based on the sandwich principle, which uses antibodies to hCG labeled with an enzyme or a conventional or luminescent dye.
When test gives two lines it means Positive even though the 2nd line was really faint, you could barely see it and also considered Positive.
Interpretations of hcg beta subunit levels:
Serum quantitative HCG measurement is the most accurate than urine, but many error factors could alter the results.
The chart of hCG levels can give sharp indicators of progression of pregnancy.
False Positive and false negative results:
- Total hCG levels may vary in a very wide range within the first 4 weeks of gestation, leading to false results during this period of time.
- Elevated hCG readings in the absence of pregnancy: Gestational trophoblastic 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.
- Random urine samples: due to dilution of the urine content during the day, the hCG level may be not clearly detected in urine sample especially in the beginning of the gestation “Early in pregnancy” , it is recommended to send first morning sample to the lab for testing beta-subunit hCG.
- Serum b-hCG tests is more sensitive and accurate than rapid tests used in home or physician office, because The medical lab tests employ a monoclonal antibody techqniques, 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.
- People may be confused about the correlation of hCG with other hormones, I mean LH and FSH, The latter two are always present at varying levels in the body, nevertheless the presence of hCG must indicate pregnancy.
- Example: My wife’s lab results-HCG Subunit serum beta qual test is -ve and the Preg Urine test was +ve. Is she pregnant. It has been 3 weeks since she missed her periods. In the last 2 days, 3 home pregnancy tests came back not pregnant. The Lab results were done within a week of her missing her period. Solution: Wait 2 days more or the doctor needs to do a quantitative hcg level this will give the number of hcg not just Positive/negative results or an ultrasound will resolve it.