LH surge in the menstrual cycle triggers:

The menstrual cycle is regulated by a complex interplay of hormones from the hypothalamus, anterior pituitary, and ovaries. 1. **Follicular Phase**: FSH (Follicle Stimulating Hormone) stimulates the growth of follicles. As follicles grow, they secrete estrogen. 2. **The Surge**: Once estrogen levels reach a critical threshold, they exert a positive feedback effect on the anterior pituitary, causing a massive release of Luteinizing Hormone (LH). This is known as the **LH surge**. 3. **Ovulation**: The LH surge occurs around the middle of the cycle (day 14 in a 28-day cycle). This sudden spike in LH triggers the final maturation of the Graafian follicle, its rupture, and the release of the secondary oocyte into the fallopian tube. This process is called **ovulation**. 4. **Luteal Phase**: The ruptured follicle then transforms into the corpus luteum, which secretes progesterone to maintain the uterine lining. Therefore, the LH surge is the specific hormonal trigger for ovulation.