A surge in LH triggers which event in the menstrual cycle?

• A. Ovulation
• B. Menstruation
• C. Fertilization
• D. Implantation

Answer: (A)

The surge in luteinizing hormone drives ovulation—the release of the mature egg from the ovarian follicle into the fallopian tube. This spike is triggered by rising estrogen from the maturing follicle, which flips the feedback on LH and mounts a brief, strong release of LH at mid-cycle. The LH surge also promotes the transformation of the ruptured follicle into the corpus luteum, which then secretes progesterone to prepare the uterine lining for possible implantation. If fertilization doesn’t occur, progesterone falls and menstruation begins. Fertilization and implantation happen after ovulation but are not direct effects of the LH surge itself.