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What hormonal changes cause the surge in luteinizing hormone before ovulation?

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Detailed cross-sectional illustration of a human ovary showing the stages of follicle development, ovulation, and corpus luteum formation, with labeled structures including primordial, primary, secondary, and mature follicles, a ruptured follicle releasing an ovum, and corpus luteum and albicans. An inset at the bottom shows the ovary's location in the female reproductive system. — ovary The steps of ovulation, beginning with a dormant primordial follicle that grows and matures and is eventually released from the ovary into the fallopian tube.

The surge in luteinizing hormone (LH) that triggers ovulation is primarily driven by the hormonal feedback loop between the ovaries and the pituitary gland.

During the proliferative phase of the menstrual cycle, the developing ovarian follicle secretes estrogens, specifically estradiol. While these estrogens generally exert a negative feedback effect by inhibiting the output of follicle-stimulating hormone (FSH), they are also believed to stimulate the release of LH from the pituitary gland.1

This process is part of a complex regulatory system where the pituitary gland initially stimulates the ovary, and the ovary subsequently influences the pituitary's hormonal output. The basic rhythm of this cycle is ultimately under the control of the hypothalamus, which releases substances that trigger the secretion of gonadotropic hormones like LH and FSH. The sequential action of these hormones leads to the ripening of the follicle and the eventual release of the egg at mid-cycle.1