Going back to any textbook on obstetrics and gynecology or endocrinology published in the 1970s, the chapter on endocrinology of the placenta was clearly defined and limited. In the recent past the vast majority of medical students throughout the world simply learned that protein (hCG, hPL) and steroid (progesterone, estradiol, estriol) hormones are the major products of human trophoblast. Even though it was stated that they play a role in the maintenance of pregnancy, for several years the investigations on the endocrine function of human placenta did not show a significant development. At that time the fetal membranes (amnion and chorion) and maternal decidua had no endocrine relevance: they represented an anatomical interface expressing some capacity for producing prostaglandins.
Starting from the studies by Khodr and Siler-Khodr (1) and by Krieger et al. (2), the interest on placental hormones was renewed. Their studies on placental gonadotropin-releasing hormone (GnRH) and on