What surge triggers ovulation?

• A. LH surge resulting in release of egg (oocyte)
• B. FSH surge
• C. Progesterone surge
• D. Estrogen surge

Answer: (A)

Ovulation is triggered by a surge of luteinizing hormone (LH) from the anterior pituitary. As a mature follicle produces more estrogen, this rising estrogen exerts positive feedback on the hypothalamus and pituitary, causing a sharp LH peak just before mid-cycle. That LH surge prompts the final maturation of the follicle and rupture of its wall, releasing the oocyte.

FSH supports follicle growth and estrogen production but does not initiate the release. After ovulation, the corpus luteum forms and produces progesterone to support the luteal phase; thus a progesterone surge occurs after ovulation, not to trigger it. Estrogen levels rise before ovulation and help drive the LH surge, but the actual trigger for ovulation is the LH surge.