Menstrual cycle between 45 and 55 years of age. Bleeding usually lasts around 2 to 7 days. The menstrual cycle is governed by hormonal changes. These changes can be altered by using hormonal birth control to prevent pregnancy. Each cycle can be divided into three phases based on events in the ovary (ovarian cycle) or in the uterus (uterine cycle). The ovarian cycle consists of the follicular phase, ovulation, and luteal phase whereas the uterine cycle is divided into menstruation, proliferative phase, and secretory phase. Stimulated by gradually increasing amounts of estrogen in the follicular phase, discharges of blood (menses) flow stop,
Breast development the breasts by inducing the expression of the progesterone receptor (PR) in breast epithelial tissue. In contrast to the case of the PR, ER expression in the breast is stable and differs relatively little in the contexts of reproductive status, stage of the menstrual cycle, or exogenous hormonal therapy. During pregnancy, pronounced breast growth and maturation occurs in preparation of lactation and breastfeeding. Estrogen and progesterone levels increase dramatically, reaching levels by late pregnancy that are several hundred-fold higher than usual menstrual cycle levels. Estrogen and progesterone cause the secretion of high levels of prolactin from the anterior pituitary, which