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How do birth control pills affect FSH and LH hormones?

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Blister pack of 28 oral contraceptive pills arranged in four rows, with 21 white active pills followed by 7 orange inactive pills. Arrows indicate the order for taking pills. — birth control A 28-day package of birth control pills.

Birth control pills, which are synthetic steroid hormones, function primarily by suppressing the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the pituitary gland.12

In a natural cycle, FSH and LH stimulate the ovaries to release estrogen and trigger ovulation. By maintaining consistent levels of synthetic hormones, birth control pills—particularly combination pills containing both estrogen and progestin—exert a negative feedback effect that lowers the levels of FSH and LH.1234

When these gonadotropic hormones are suppressed, the ovaries do not receive the necessary signals to mature and release an egg, thereby preventing fertilization. While progestin-only pills also contribute to this suppression, they additionally work by thickening cervical mucus to create a barrier against sperm.123