Which hormone level rises prior to ovulation?

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

Answer: (A)

During the late follicular phase, the developing follicle secretes increasing amounts of estrogen. This rise reaches a peak just before ovulation and shifts estrogen’s feedback from negative to positive on the hypothalamic–pituitary axis. That positive feedback drives a surge of GnRH and, in turn, a surge of LH from the pituitary. This LH surge is the actual trigger for ovulation, causing the mature follicle to release the egg. After ovulation, progesterone rises from the corpus luteum to support the luteal phase and potential implantation. Testosterone is present but does not drive ovulation in the same way estrogen does.