Estrogen and Progestogen Receptor Levels in Different Types of Mid‐Secretory Endometrium

Abstract Human endometrial estrogen and progestogen receptor levels in the mid‐secretory phase were determined in various types of endometrium to contribute to a better understanding of luteal insufficiency. The concentrations of both total estrogen and progestogen receptor sites (both cytosol and nuclear; both occupied and unoccupied) decreased in the out‐of‐phase endometrium (p<0.025) and tended to decrease in the hypoplastic uterine endometrium, compared with those of the in‐phase endometrium. However, serum steroid levels in both groups showed no difference. The findings suggest that being out of phase reflects the indigenously reduced number of endometrial cellular receptors. This hypothesis would seem to aid our understanding of the hypoplastic uterus. Clomiphene treatment during the luteal phase changed the out‐of‐phase endometrium to in‐phase endometrium in some cases (19 out of 36); in these cases, the endometrial steroid receptor levels reached the levels attained in the in‐phase endometrium and the gonadotropin secretion was stimulated to greater than the controls, resulting in increased steroid synthesis.