What hormone surge triggers ovulation?

The hormone responsible for triggering ovulation is luteinizing hormone (LH). In the menstrual cycle, just prior to ovulation, there is a rapid increase or "surge" in LH levels that is crucial for the release of the mature egg from the ovary. This LH surge is stimulated by high levels of estrogen produced by the growing follicle, which signals the brain to release more luteinizing hormone from the pituitary gland.

Ovulation typically occurs about 24-36 hours after the LH surge, marking the transition from the follicular phase to the luteal phase of the cycle. This hormonal event is a critical part of female fertility, as it indicates that an egg is available for fertilization.

The other hormones listed play significant roles in the menstrual cycle, but they do not directly trigger ovulation in the same way as LH. Follicle-stimulating hormone (FSH) is important for stimulating follicle growth, estrogen helps to regulate the cycle and prepare the uterine lining, and progesterone is key for maintaining the luteal phase if pregnancy occurs. However, it is the surge in LH that is specifically responsible for the event of ovulation itself.