Endometrial oestrogen and progesterone receptors and their relationship to sonographic endometrial appearance

The present study was undertaken to evaluate a possible relationship between the endometrial concentrations of oestrogen receptor (ER) or progesterone receptor (PR), and the sonographic appearance of human endometrium. Sonographic assessments and aspirations of the endometrium at the time of or prior to ovulation were made in 48 cycles of 45 infertile women. Endometrial patterns were classified as A, triple line pattern, or B, not triple line, on the basis of echogenicity. We did not find a correlation between ER or PR and serum oestradiol or endometrial thickness. Furthermore, serum oestradiol concentrations were not correlated with endometrial pattern or thickness. The only significant correlations were found between the concentrations of ER and PR in the pattern A endometrium (r = 0.80, P < 0.01) and in the pattern B endometrium (r = 0.49, P < 0.05). There were no differences in the mean concentrations of ER and PR despite differences in endometrial pattern and thickness. However, PR was measured at >800 fmol/mg protein in 12 out of 38 pattern A endometria, while PR was <800 fmol/mg protein in all pattern B endometria. These data suggest that high PR expression in the pre-ovulatory period is related to an adequate endometrial growth and thereby increases the responsiveness of the endometrium to progesterone stimulation after ovulation.