A progesterone and androgen receptor antagonist (IC50s = 0.51 and 0.12 nM for isolated rabbit uterus and rat prostate cells, respectively) and an active metabolite of desogestrel, increases endometrial and myometrial vascularization, uterine weight, and uterine artery length, as well as decreases the number of hormone-secreting corpus luteal glands in non-ovariectomized guinea pigs when administered subcutaneously as a 1 mm sustained-release pellet
