HCG, also known as human chorionic gonadotropin, is a glycoprotein secreted by embryonic trophoblast cells, which usually has the following roles: 1, protection of embryo: HCG can be adsorbed on the surface of trophoblast cells to avoid embryonic trophoblast cells being attacked by maternal lymphocytes; 2, fetal preservation treatment: if HCG is insufficient to cause preterm abortion, HCG can be injected to preserve fetus, and HCG injection for women who are not pregnant can promote ovulation; 3, other roles: HCG can maintain the life span of menstrual corpus luteum, and promote sexual differentiation and gonadal development. 3.Stimulate androgen secretion: HCG can stimulate fetal testes to secrete testosterone, promote sexual differentiation and gonadal development; 4.Other effects: HCG can maintain the life span of menstrual corpus luteum, make menstrual corpus luteum increase to become pregnancy corpus luteum, promote the conversion of androgen aromatization to estrogen, and stimulate the formation of progesterone at the same time. By detecting HCG value, it also has the role of determining whether pregnancy or other diseases, mainly as follows: 1. Pregnancy detection: HCG can determine whether pregnancy, but also has a certain suggestive effect on ectopic pregnancy; 2. Detection of birth control: if HCG value continues to fall, it suggests that it is not suitable to continue birth control and consider stopping pregnancy; when HCG value keeps rising, it suggests that birth control is successful; 3. Detection of abortion: HCG test is positive when surgical abortion is incomplete, and HCG turns from positive to negative when complete abortion or stillbirth; 4. Detection of other diseases: such as choriocarcinoma, gravida, etc. It also has a certain suggestive effect on ovarian cysts, uterine cancer and other diseases.