what does progestin in the birth control pill do?
Progestin is a form of progesterone, a hormone that plays a role in the menstrual cycle and pregnancy. Progestin is. used in combination with another hormone called estrogen in combined hormonal birth control pills, the vaginal ring, and. the skin patch. It also can be used by itself in progestin-only pills and the birth control injection. The birth control implant.