Human chorionic gonadotropin

Human chorionic gonadotropin interacts with the LHCG receptor of the ovary and promotes the maintenance of the corpus luteum during the beginning ofpregnancy. This allows the corpus luteum to secrete the hormone progesterone during the first trimester. Progesterone enriches the uterus with a thick lining of blood vessels and capillaries so that it can sustain the growing fetus. Due to its highly negative charge, hCG may repel the immune cells of the mother, protecting the fetus during the first trimester It has also been hypothesized that hCG may be a placental link for the development of local maternal immunotolerance[citation needed]. For example, hCG-treated endometrial cells induce an increase in T cell apoptosis (dissolution of T cells). These results suggest that hCG may be a link in the development of peritrophoblastic immune tolerance, and may facilitate the trophoblast invasion, which is known to expedite fetal development in the endometrium.It has also been suggested that hCG levels are linked to the severity of morning sickness or Hyperemesis gravidarum in pregnant women.
Because of its similarity to LH, hCG can also be used clinically to induce ovulation in the ovaries as well as testosterone production in the testes. As the most abundant biological source is women who are presently pregnant, some organizations collect urine from pregnant women to extract hCG for use in fertility treatment.
Human chorionic gonadotropin also plays a role in cellular differentiation proliferation and may activate apoptosis.