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What causes the luteinizing hormone surge before ovulation?

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Diagram of the menstrual cycle showing hormone levels, follicle development, and endometrial changes across 28 days. It highlights menstruation, ovulation, and the follicular and luteal phases, with labeled curves for estrogen, progesterone, FSH, and LH. — menstruation Cyclical changes during a woman's normal ovulatory menstrual cycle.

The surge of luteinizing hormone (LH) that triggers ovulation is primarily driven by the ovary through a feedback mechanism involving estrogen.

During the follicular phase of the menstrual cycle, maturing follicles secrete increasing amounts of estradiol. As these estrogen levels rise, they stimulate the pituitary gland to increase the secretion of LH. This process is further supported by the secretion of small amounts of progesterone from the follicles. Together, these rising hormone levels trigger a transient, significant surge in LH (and to a lesser extent, follicle-stimulating hormone), which causes the mature Graafian follicle to rupture and release the egg.123

While the pituitary gland is responsible for releasing these hormones, the overall rhythm of the cycle is governed by the hypothalamus, which coordinates the complex interplay between the brain and the ovaries.23