Horacio Bruno Croxatto

The Demonstration of the Antiprogestin Effects of RU 486 when Administered to the Human during hCG-Induced Pseudopregnancy

In the absence of fertilization, there is a progressive decrease in circulating progesterone levels towards the end of the luteal phase which leads to endometrial bleeding. If implantation occurs, however, human chorionic gonadotropin (hCG) from the developing trophoblast stimulates progesterone secretion from the corpus luteum. This prevents shedding of the endometrium during early pregnancy. The administration of exogenous hCG to normal women during the luteal phase simulates early pregnancy. This model has been used to study the action of drugs that interfere with progesterone synthesis, secretion or peripheral action.