Estrogen receptor in human endometrium during the menstrual cycle and early pregnancy

Available estrogen receptor has been estimated in endometrial tissue obtained from 8 women on the eighth and twenty-first days of the same menstrual cycle. Respective concentrations were 3.8 ± 1.1 and 6.0 ± 2.5 femtomoles (fmoles) per milligram of wet tissue during 5 ovulatory cycles and were 8.1 ± 3.7 and 2.9 ± 0.3 fmoles per milligram during 3 anovulatory cycles. The latter cycles appear to be associated with elevated endometrial receptor concentration on Day 8, and a marked drop between Days 8 and 21. In decidual tissue obtained from 4 patients who were 9 to 18 weeks pregnant, receptor concentration is low. The data indicate that available receptor concentration in human endometrium changes with hormonal status.