Menopause is the time when a woman's menstrual periods stop and her ovaries stop releasing eggs. A woman is considered menopausal once she has gone a year without having a menstrual period. Therefore, the exact time of a woman's final menstrual period can only be pinpointed by counting backwards after the fact.
Although most women go through menopause around age 50, normal menopause can happen any time between the age of 40 and 60. The last periods are usually more irregular and have less blood flow. However, some women's periods don't change at all.
Along with normal or natural menopause, there is also premature menopause. Premature menopause occurs before the age of 40 and can be caused by a variety of things, such as removal of the ovaries, autoimmune disorders, endocrinological reasons, or cancer therapy. Medical interventions, such as a hysterectomy (when the uterus is removed), may also prevent menstruation. If the ovaries are removed as well, production of the hormones estrogen and progesterone are stopped, causing the symptoms of menopause.