Human Chorionic Gonadotropin
- Shortly after the developing embryo implants into the endometrium it begins secretion of the hormone human chorionic gonadotropin (hCG)
- hCG is secreted during the first 8-10 weeks of pregnancy
- The role of this hormone is to:
- Stimulate the corpus luteum in the ovary to maintain secretion of oestrogen and progesterone (in order to continue the development of the endometrium)
- Stimulate the growth of the placenta and uterine enlargement
- Inhibit menstruation
- During the second trimester (after 12 weeks) hCG declines and the placenta takes over the role of stimulating the secretion of oestrogen and progesterone
- Pregnancy tests detect the presence of hCG in the mother's urine and can be used to confirm a positive pregnancy
Hormone changes during pregnancy graph
hCG increases during the first 12 weeks of pregnancy to stimulate the release of oestrogen and progesterone; after 12 weeks hCG declines as the placenta takes over
Pregnancy tests
- The confirmation of a pregnancy during the early stages can be through the presence of hCG
- This is detected in the the mother's blood and urineĀ
- A pregnancy test kit makes use of a specific type of antibody called a monoclonal antibody (mAb) which is used to detect the presence of hCG
- Monoclonal antibody is a single antibody that can be used outside of the body and will react to a specific antigen, in this hCG
- When using a pregnancy test the mother will urinate onto the test strip, the urine will contain higher levels of hCG if the mother is pregnant
- The urine, containing the hCG will travel along the test strip of the pregnancy test; the test strip contains the monoclonal antibodies which bind to the hCG (if present) and lead to a colour change within the pregnancy test which can be seen and inform the mother that she is pregnant
- If there is no colour change it means that hCG is not present (in high enough concentrations) to bind to the monoclonal antibodies and give the colour change
Pregnancy test diagram
Monoclonal antibodies are used to detect the presence of the hormone hCG in the urine of pregnant women