How does estrogen change the uterine lining during the menstrual cycle?

During the menstrual cycle, estrogen plays a critical role in building and maintaining the endometrium, the mucous membrane lining the uterus.2

Following menstruation, the endometrium is thin. As ovarian follicles mature during the proliferative phase, they secrete estradiol, which stimulates the endometrium to thicken and become more vascular. Specifically, estrogen increases the endometrium's size, weight, cell number, blood flow, protein content, and enzyme activity. Under this influence, the uterine glands become taller.12

These changes are essential for preparing the uterus to receive a fertilized ovum. If fertilization does not occur, the corpus luteum eventually degenerates, leading to a drop in estrogen and progesterone levels. This withdrawal causes the endometrial blood vessels to constrict, resulting in the shedding of the uterine lining during menstruation.314