Menopause is a change that occurs when a woman’s body no longer releases eggs, and her ovaries produce significantly lower amounts of the hormones estrogen and progesterone. It typically occurs between the ages of 45 and 55 years, although it can occur earlier or later in a woman’s life. The average age of menopause in the United States is 51 years. Menopause is officially said to have occurred when a woman does not have a menstrual cycle (also known as a period) for 12 consecutive months and there are no other causes for this change.

During a woman’s reproductive years, a gland in the brain produces hormones (substances sometimes called the body’s “chemical messengers”) that cause a new egg produced by the ovaries to be released from its follicle (sac). This occurs at approximately the same time each month. As the follicle develops, it produces estrogen and progesterone, which help prepare the body to receive and nourish a fertilized egg (zygote). When fertilization does not occur, estrogen and progesterone levels drop. This causes the lining of the uterus to break down, and the result is menstruation.

During menopause – sometimes referred to as “the change” or “change of life” – a woman’s body no longer releases eggs, and her ovaries substantially reduce production of the hormones estrogen and progesterone. This can cause many side effects, including hot flashes, vaginal dryness and thinning of the bones (osteoporosis). In addition, women report a lower sex drive and feelings of depression. To relieve these symptoms, many women choose to take medications known as hormone replacement therapy (HRT). This can involve taking synthetic estrogen, which is often combined with synthetic progesterone, known as progestin. HRT has become controversial over the past years due to its association with an increased risk for breast cancer. However, HRT may help prevent bone loss and heart disease, especially if started before age 60. A woman and her physicians can best determine if HRT is a viable treatment in menopausal and postmenopausal years.

Although menopause usually occurs because of the natural aging process, other factors can also trigger the event at younger ages. Surgery to remove both ovaries (bilateral oophorectomy) will cause premature ovarian failure. Genetic factors and cancer treatments such as chemotherapy or radiation therapy to the pelvic area also can cause early menopause.

In addition, a new study that analyzed data from the renowned Framingham Heart Disease Epidemiology Study found that certain risk factors for heart disease (e.g., high cholesterol levels, excess weight, high blood pressure) can lower the age at which women reach menopause.

Traditionally, menopause has been viewed as the end of a woman’s ability to conceive. However, many women have erratic menstrual cycles in the period leading up to menopause, known as perimenopause. This can make the exact date of menopause difficult to pinpoint, and it is possible for women considered to be postmenopausal to conceive a child. In addition, recent advances in medical technology are allowing more menopausal and postmenopausal women to become pregnant (e.g., through use of a donor egg).

There are about 37.5 million women reaching or currently at menopause (ages 40 to 59 years) in the United States, according to data collected as part of the census in 2000. Because of increased life expectancy, women today may live as much as one-third to one-half of their lives after menopause. For this reason, women must be careful to take steps that can help them live healthy, productive lives during these years.