[Endometrial steroid receptor during normal menstrual cycle and physiopathology of nidation]

Human uterine endometrial steroid receptor [estrogen (ER), progestin (PR) and androgen (AR) receptors] in the normal menstrual cycle were determined at the cellular level. Endometria with pathological out-of-phase findings or with hypoplastic uterus were evaluated for the concentration of steroid receptors, for a better understanding of their pathophysiology. ER and PR levels gradually rose toward the early secretory phase, remained at the maximum level during the mid-secretory phase and dropped to the lowest level during the late secretory phase. Especially nuclear PR reached the maximum level during the mid-secretory phase. These results indicate that the endometrial ER and PR, especially the endometrial nuclear PR, is kept in the maximum level at implantation. AR showed only a slight change in a very low level throughout the menstrual cycle. This indicates that androgen may not play so important a role in endometrial physiology. Endometria with out-of-phase or with hypoplastic uterus contained significantly low levels of endometrial ER and PR, while serum hormones levels were normal. This indicates indigenous reduction of ER and PR synthesis in such endometria.