A tendency of increased ESR1 expression was also seen in the endometrial tissues of young women with endometriosis compared to women without endometriosis in the proliferative (1.44-fold increase; adjp = 0.0508) and secretory (2.2-fold increase; adjp = 0.0584) menstrual cycle phases (Figure 3c). Here, ESR1 is linked to endometriosis.