When does the secretion of HCG primarily occur?

The secretion of human chorionic gonadotropin (HCG) primarily occurs if fertilization of the ovum takes place. After a sperm successfully fertilizes an egg, the resulting zygote begins to divide and form into an embryo. Once implantation of the embryo in the uterine lining occurs, the placenta starts to develop and produces HCG. This hormone plays a crucial role in maintaining the corpus luteum, which in turn helps sustain early pregnancy by ensuring the continued production of progesterone and estrogen. These hormones are necessary for creating an environment conducive to embryo growth and development.

Understanding the role of HCG is significant, particularly in the context of pregnancy tests, which measure HCG levels to confirm pregnancy. HCG does not play a role during menstruation, after ovulation before fertilization, or during the follicular phase, as its main function is linked to the presence of a fertilized egg and subsequent pregnancy.