The endometrium undergoes changes throughout a woman's menstrual cycle, under the influence of ovarian hormones. The menstrual cycle begins with the onset of menstruation, when the endometrium is shed and eliminated, as it will regenerate during the menstrual cycle that is beginning.
In the proliferative phase, the number of cells in the stroma and endometrial glands increases. This phase lasts until the time of ovulation. Once the woman has ovulated, the secretory phase begins due to the action of progesterone. In this phase the endometrial glands secrete substances that will be necessary for embryo implantation to take place.
If pregnancy does not occur, the endometrium will be shed and eliminated with the next menstrual period.