Progestin receptor levels in endometria with delayed or incomplete secretory changes

In women with an infertility problem, cytosol progestin receptors were quantified in endometrial biopsies and correlated to histologic postovulatory dating. In 19 women (group A) the histologic dating corresponded to the cycle day; 14 women (group B) showed delayed or incomplete secretory changes. Group B showed significantly lower mean progestin receptor values (132 +/- 22 fmoles/mg protein [+/- SEM, P less than .01] ) than group A (236 +/- 29 fmoles/mg protein). The mean serum progesterone values did not differ significantly between groups A and B in the midluteal or the late luteal phase of the cycle. Inadequate maturation of the endometrium seems to correlate with insufficient development of progestin receptor binding sites rather than with decreased serum progesterone levels.