Which hormone primarily triggers ovulation?

Luteinizing hormone (LH) is the primary hormone that triggers ovulation. During the menstrual cycle, a surge in LH levels occurs mid-cycle, leading up to ovulation. When the estrogen produced by the developing follicles reaches a certain threshold, it stimulates the anterior pituitary gland to release a substantial amount of LH. This sudden increase in LH causes the mature ovarian follicle to release an egg, which is the process known as ovulation.

While follicle-stimulating hormone (FSH) plays a role in the initial stages by promoting the growth and maturation of ovarian follicles, it is the LH surge that is crucial for the actual release of the egg. Estrogen is involved in the feedback mechanism that leads to the LH surge, and progesterone is important for preparing the uterine lining for potential implantation after ovulation, but it does not directly trigger ovulation itself. Thus, LH is the key hormone responsible for this critical event in the menstrual cycle.