Human chorionic gonadotropin Hormone
Human chorionic gonadotropin Hormone
Human chorionic gonadotropin (HCG) is a pregnancy hormone secreted by the placenta. Its production stimulates ovarian progesterone secretion.
When an embryo develops, it begins to produce HCG, which aids in the production of other important pregnancy hormones such as progesterone and estrogen. This causes the uterine lining to thicken and increase blood supply so that the embryo can be received and fed after implantation. The proper balance of these essential hormones is critical for a healthy pregnancy and baby development.
Adequate progesterone levels are required for successful implantation and to prevent further egg release from the ovary.
The glycoprotein human chorionic gonadotrophin has alpha and beta subunits.
The beta subunit is specific for HCG and does not cross react with the alpha subunit of Leutenizing hormone, It can be found in urine, blood, and amniotic fluid.
The serum and urine levels rise rapidly during pregnancy, peaking at six to eight weeks and then gradually declining.
When a woman becomes pregnant, her body undergoes numerous changes. One of the most rapid changes in HCG production.
The hormone first appears in the urine ten days after the woman conceives. Home pregnancy tests detect the presence of HCG in the urine. This test can be accurate if used correctly.
Urine tests do not reveal how much HCG is in your body. They only know if a woman is pregnant if her HCG levels are high enough to support a chemical reaction that confirms fertilization.
Human chorionic gonadotropin Hormone detection in the Laboratory
We detect Human chorionic gonadotropin hormone by this two Specimen:
When you take a urine sample to the Pregnant mother , the HCG in her urine reacts with the pregnancy test strip . Laboratory Pregnancy tests react to HCG levels in urine.
Also if the HCG concentration in the urine is high enough, the pregnancy test will show double vertical lines.
The enough HCG concentration, some tests will also show “pregnant.” Your blood will be drawn and sent to the lab for a blood test.
The concentration of HCG in the blood sample will be determined by the lab. They will confirm the pregnancy if the concentration is high enough.
Laboratory tests for pregnancy are based on the detection of human chorionic gonadotrophin hormone in serum or urine; mainly there are two types of test:
- Biologic animal Bioassay (A-Z test)
This test is carried out on laboratory animals (female mouse). For example, the patient’s urine is injected into a female mouse after a certain period, the mouse is killed, and the ovary is examined for signs of pregnancy. This test, however, cannot be used to make an early diagnosis.
Furthermore, it is time consuming and necessitates a steady supply of laboratory animals.
- Immunologic Tests
Immunologic Tests can be both qualitative and quantitative in nature.
The qualitative estimation of HCG in urine is used for pregnancy detection and confirmation. In cases of preeclamptic toxemia, hydatidiform mole, and choriocarcinoma, quantitative estimation of HCG in serum is useful.
A quantitative immunological method for detecting chorionic gonadotrophin (HCG) in human urine has been described. The method can be used for quantitative determinations of HCG in urine and is useful as a simple and quick pregnancy test.
Immunologic testing is less expensive and faster than biologic animal testing.
An early morning urine specimen is preferable because this is the most concentrated and contains the highest level of HCG.
However, specimen collected at any time may be used with a specific gravity at least 1.010.
Urine must be collected in a clean detergent free container. If it cannot be tested immediately, it should be refrigerated at 40C for not longer than 48 hours.
Specimen preserved with boric acid is also suitable for testing. When tested, the urine and test reagents should be at room temperature. If the urine is cloudy it should be filtered or centrifuged and the supernatant fluid used.
Specimens that are heavily contaminated or contains large amount of proteins or blood, are not usually suitable for testing.
There are two types of immunologic test commonly available and provided in a form of kit.
Rapid latex slide test: have two types
- Indirect latex slide test
- Direct latex slide test
1. Indirect latex slide test
The urine sample is first treated with anti-HCG before being reacted with the latex suspension.
If the urine contains HCG, the anti HCG will be neutralized, and the latter will be unavailable to the HCG coated latex particles for agglutination.
Materials and reagents: Antiserum containing HCG antibody. HCG-coated latex reagent. There are both positive and negative controls. Sticks and slides for mixing
Procedure Note: It is best to refer to the manufacturer’s manual in all cases
.1. Place one drop of urine sample on the ring of the slide provided by the manufacturer.
- Place one drop of anti-HCG reagent on the slide with the urine specimen. Using an applicator stick, thoroughly combine the two fluids.
Note. To maintain the same volume, always hold the dropper in the same vertical position and use the same type of dropper for both the urine specimen and the antiserum.
- Gently rock the slide for about 30 seconds.
- Gently shake the latex antigen vial before adding one drop.
- Remix with an applicator stick and check for agglutination after 2 minutes under a bright light.
2. Direct latex slide test
The reaction is based on the interaction of HCG in urine and latex particles coated with anti HCG. Agglutination will be observed .
Pregnancy tests are usually ordered to investigate conditions such as:
- Ectopic pregnancy
- Threatened abortion
- Early pregnancy
- Hydatiform mole
- It is also used to determine whether a woman of childbearing age is pregnant before undergoing medical or surgical investigation, x-ray, or drug therapy that could harm an embryo.
Factors Influencing Pregnancy Tests
The following are the factors influencing Pregnancy test:
- Reading error – incorrect interpretation
- Expiration date of Kit
- Too long collection of urine
- Too diluted urine -falsely low HCG levels may be caused by diluted urine (low specific gravity)
- Ectopic pregnancy implantation of the ovum outside the uterine cavity.