MPA (Medroxyprogesterone acetate) is a steroidal progestin, a synthetic variant of the steroid hormone progesterone. It is used as a contraceptive, in hormone replacement therapy and for the treatment of endometriosis as well as several other indications. MPA is used to treat abnormal menstruation or irregular vaginal bleeding. MPA is a more potent derivative of its parent compound medroxyprogesterone (MP). While medroxyprogesterone is sometimes used as a synonym for medroxyprogesterone acetate, what is almost always being referred to is MPA and not MP It is on the World Health Organization's List of Essential Medicines, the most important medication needed in a basic health system.