[The endocrine capacity of the mammalian blastocyst. II. Biosynthesis and estrogen metabolism].

Among the studies realized in preimplanted embryos, draw attention to its endocrine capacity to synthesize steroid hormones: progesterone, progestins and several estrogens, which may influence locally the properties of the oviduct and endometrium creating and appropriate environment for its nutrition, migration and further development in order to let its implantation in the maternal uterus. Among the steroids secreted by the conceptus, estrogens are of special interest because of their potential importance in the biochemical events associated with the process of implantation. The purpose of this review is to contribute to the knowledge of the biosynthesis and metabolism of estrogens realized by the early embryo.