However, Lessey B. A. et al. reported that certain types of uterine receptivity defects such as endometriosis, luteal phase defect and polycystic ovarian syndrome may be caused by the loss of appropriate ERα down-regulation in endometrial epithelial cells during the mid-secretory phase, leading to defects in uterine receptivity28. Here, ESR1 is linked to endometriosis.