Pregnancy Tests Rely On The Detection of Human Chorionic Gonadotropin (hCG)
Definition
Human chorionic gonadotropin (hCG)
Human chorionic gonadotropin (hCG) is a hormone essential for sustaining early pregnancy. It ensures that the uterine environment remains suitable for the developing embryo by maintaining the production of progesterone.
- hCG is a hormone produced by the developing embryo and placenta.
- It is essential for maintaining early pregnancy by stimulating the corpus luteum to secrete progesterone.
How is hCG produced?
- Fertilization and Early Development
- After fertilization, the zygote divides and forms a structure called the blastocyst.
- The outer layer of the blastocyst, called the trophoblast, eventually develops into the placenta.
- Role of the Placenta
- The trophoblast begins secreting hCG around 6–7 days after fertilization, just before implantation.
- hCG signals the corpus luteum in the ovary to continue producing progesterone, preventing the uterine lining from breaking down.
Without hCG, the corpus luteum would degenerate, leading to menstruation and the loss of the embryo.
Why is hCG Important?
- Maintains the Uterine Lining: hCG ensures the endometrium remains thick and nutrient-rich, supporting the embryo.
- Supports Placental Development: hCG helps the placenta grow and function effectively.
In IVF treatments, hCG is often administered to trigger ovulation and support early pregnancy.
How Pregnancy Tests Work
- Pregnancy tests detect hCG in urine using monoclonal antibodies.
- Antibodies that are identical and specific to a single antigen, produced by a single clone of cells.
- hCG is specifically used because it is uniquely produced by the developing embryo and placenta shortly after fertilization, making it an early and reliable marker of pregnancy.
- Its presence in urine or blood provides a clear signal that implantation has occurred.
Definition
Monoclonal antibodies
Monoclonal antibodies are lab-engineered antibodies designed to bind to a specific target—in this case, hCG.
Remember: antibodies are proteins that recognize and bind to specific molecules, called antigens.
The Structure of a Pregnancy Test
A typical pregnancy test stick has three key zones:
- Reaction Zone
- Contains free monoclonal antibodies that bind to hCG.
- These antibodies are linked to a colored dye.
