ENDOMETRIAL ESTROGEN AND PROGESTERONE RECEPTORS WITHIN 2-14 DAYS OF MISSED MENSES IN THE HUMAN

Serial changes in the endometrial levels of estrogen and progesterone receptors (ER and PR) were measured in 50 women from days 2 to 14 of m issed menses and correlated with the plasma concentrations of hCG, pro gesterone and 17beta-estradiol. Both ER and PR of nuclei were higher t han cytosolic proteins, with a shift in the ratio of nER/nPR to nPR fr om 4th day after missed menses. On Scatchard analysis of the cytosolic and nuclear binding proteins, two classes of proteins, corresponding to Type I and II, were found. While the increasing levels of hCG maint ained luteal secretion of progesterone and 17beta-estradiol at normal mid-luteal phase levels, a gradual increase in 17beta estradiol from 9 th day of missed menses was noted. This delicate balance between circu lating levels of progesterone and 17beta-estradiol and their nuclear r eceptors at early stages of pregnancy may be of significance.