This document provides an overview of menstrual physiology and the normal menstrual cycle. It describes: - Puberty and the events leading to menarche in the hypothalamus, pituitary, and ovaries. - What is considered normal for menarche, menstrual cycle length and regularity, blood loss, and menopause based on evidence and large studies. - The stages of reproductive aging in women from the reproductive years to menopause based on a 10 stage classification system.