Particular functions of estrogen and progesterone in establishment of uterine receptivity and embryo implantation.

The process of embryo implantation requires synchronized development of blastocyst and timely establishment of uterine receptivity. Establishment of uterine receptivity, preimplantation embryo development and embryo implantation events are mainly regulated by certain factors, including cytokines, chemokines, growth factors and steroid hormones. Recent studies suggest that steroid hormones, especially estrogen and progesterone, play important roles in supporting endometrial preparations to establish endometrial receptivity. Timely establishment of endometrial receptivity is a crucial process for providing successful embryo implantation. Although many investigations until now have been performed to precisely understand the effects of estrogen and progesterone on acquiring uterine receptivity and embryo implantation in humans and rodents, there are limited numbers of studies that largely focus on this subject. Therefore, in this article we discuss the studies associated with significant functions of estrogen and progesterone in establishing receptive endometrium and the process of embryo implantation in humans and rodents.