Human chorionic gonadotropin (hCG) is a hormone produced during pregnancy. It is secreted by the cells that form the placenta, which nourishes the developing fetus. hCG plays a crucial role in maintaining the production of progesterone, a hormone essential for sustaining pregnancy. In addition to its role in pregnancy, hCG is also used in medical treatments. It can be administered to stimulate ovulation in women undergoing fertility treatments and is sometimes used in men to treat certain conditions related to low testosterone levels.