Definition

A combination of two steroid sex hormones, an estrogen and a progestin, used for contraceptive purposes. Estradiol, the endogenous counterpart of ethinyl estradiol (EE), is the principal, most potent estrogen hormone produced by the ovaries and is vital to the maintenance of fertility and secondary sexual characteristics in females. Levonorgestrel is a synthetic progestogen. This drug combination prevents or delays ovulation and causes a variety of hormonal changes. Ethinyl estradiol inhibits the release of follicle stimulating hormone (FSH), thus suppressing the development of ovarian follicle; levonorgestrel inhibits the release of luteinizing hormone (LH), thus preventing ovulation. This combination of agents alters the endometrium in such a way as to discourage implantation.