Progestogen, also known as progestin, is a synthetic hormone that mimics the effects of progesterone in the body. Some common synonyms for progestogen include gestagen, gestogen, and progestacional. Other related terms include luteal hormone, corpus luteum hormone, and pregnancy hormone. Progestogens are commonly used as a form of hormonal birth control, as well as in hormone replacement therapy for menopausal women. They are also sometimes used in the treatment of certain cancers, such as breast cancer, and to help regulate menstrual periods. Progestogens work by thickening the cervical mucus to prevent sperm from reaching the egg, and by thinning the uterus lining to prevent implantation.