Used primarily in oral contraceptives, mestranol prevents ovulation by regulating hormonal activity in the female reproductive system. It works in combination with progestins to inhibit the release of eggs from the ovaries, thicken cervical mucus to block sperm, and alter the uterine lining to prevent implantation. Though largely replaced by ethinyl estradiol in modern birth control pills due to better metabolic stability, mestranol was a key component in early generations of hormonal contraceptives. It remains relevant in some formulations and in historical context for the development of hormonal therapy.