TOPICS: Progestins, levonorgestrel, medroxyprogesterone, etonogestrel, norethindrone, megestrol, progestin receptor, decreased growth of endometrium, increased vascularization of endometrium, thickened cervical mucus, oral contraception, iud, arm implant contraception, depot injection, endometrial cancer, abnormal uterine bleeding, progesterone challenge test, withdrawal bleed, normal uterine anatomy, estrogen dysfunction, antiprogestins, competitive inhibitors of progestins at progesterone receptors, mifepristone, termination of pregnancy, ulipristal, emergency contraception