Progestogens are agonists of the progesterone receptors (PRs) and produce progestogenic or progestational effects. They have important effects in the female reproductive system (uterus, cervix, and vagina), the breasts, and the brain. In addition, many progestogens also have other hormonal activities, such as androgenic, antiandrogenic, estrogenic, glucocorticoid, or antimineralocorticoid activity. They also have antigonadotropic effects and at high doses can strongly suppress sex hormone production. Progestogens mediate their contraceptive effects both by inhibiting ovulation and by thickening cervical mucus, thereby preventing fertilization. They have functional antiestrogenic effects in certain tissues like the endometrium, and this underlies their use in menopausal hormone therapy.