Abstract
Endometriosis affects fertility in many women and may partly be due to decreased endometrial receptivity. Several mechanisms have been suggested, notably, progesterone resistance for which a number of candidate biomarkers have been suggested. Here we demonstrate aberrant levels of steroid hormone receptors and the small heat shock protein αB-crystallin in eutopic endometrial epithelium from 38 women with peritoneal endometriosis diagnosed during investigation for secondary infertility. Spontaneous pregnancies within 1 year after medical and surgical treatment for endometriosis were recorded and semi-quantitative immunohistochemistry data compared between women with endometriosis who did or did not become pregnant and healthy controls. Stronger immunostaining for ER-α was detected in luminal and glandular endometrial epithelium from women with endometriosis who did not become pregnant during the post-treatment observation period versus endometriosis patients who became pregnant and controls. Staining levels of PR and PR-B were lower in patients without subsequent pregnancies than in the two other groups. Endometrial levels of αB-crystallin in endometriosis patients similar to those in controls were strongly correlated with the chance of becoming pregnant, whereas higher or lower levels were not.