What is HCG?

HCG stands for human chorionic gonadotrophin, a hormone that is produced during pregnancy. HCG is initially produced by the embryo while it is still in the development phase, and then eventually by the placenta lining the uterine wall, which serves to protect the same embryo. HCG protects the ovarian corpus luteum so that it can produce adequate amounts of the hormone progesterone, critical in maintaining a healthy pregnancy.
Pregnant women have elevated levels of HCG, and it can be detected at around 11 days after fertilization through a blood test and around 2 weeks after fertilization through a urine test. HCG levels double in number after every 72 hours, for the first 8-11 weeks of pregnancy, after which the levels begin to level off. Because pregnancy is associated with high levels of HCG, this is used as a marker for many pregnancy tests.
HCG is also used in fertility treatments, inducing ovulation for women and testosterone production in men. There has been some controversy in the use of HCG as well, as a means to lose weight, as popularized by British endocrinologist ATW Simeons. I has been theorized that introducing HCG to the body prompts it to go in protective mode for the ‘fetus’, thus mobilizing the body to consume fat deposits.