Which hormone is primarily responsible for triggering ovulation via its surge?

• A. Estrogen
• B. LH
• C. FSH
• D. Progesterone

Answer: (B)

The key idea is that a surge of a pituitary gonadotropin drives the release of the egg. In the mid-cycle, rising estrogen from the dominant follicle switches from negative to positive feedback on the pituitary, producing a sharp rise in luteinizing hormone. This LH surge acts on the mature follicle to weaken its wall and trigger ovulation, releasing the oocyte about a day later. After ovulation, the ruptured follicle becomes the corpus luteum and starts producing progesterone to support the uterine lining. While estrogen helps initiate the surge by signaling when to release more LH, the actual trigger for ovulation is the LH surge itself. FSH mainly supports follicle growth and maturation, but does not directly cause the ovulation event.