hCG

hCG (Human chorionic gonadotropin) is produced by specialized cells, called syncytiotrophoblasts, that surround the embryo. These cells create the placenta after implantation. The role of hCG is crucial in the first trimester of pregnancy, when it interacts with the ovary and promotes the maintenance of the corpus luteum (a structure that derives from the cells of the follicle, after its rupture for the egg release, during the ovulation). hCG stimulates the corpus luteum to secrete progesterone, which thickens the lining of the uterus and its capillarization, so that it can sustain the growing fetus.