Human chorionic gonadotrophin
Human chorionic gonadotrophin (HCG) is a hormone released during pregnancy. It plays a key role in pregnancy as it interacts with Leutenising Hormone (LH) receptors. This causes the corpus leuteum to remain intact, and ensures the continued production of progesterone. This in turn keeps the endometrium from disintergrating. HCG is released when an embryo is implanted into the uterus of a female by the placenta, and by structures called the chorionic villi . Cite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive title
Over the counter pregnancy tests work by detecting HCG in the urine. If a woman is pregnant then the HCG will bind to antibodies on the surface of the test thus causing a positive result.