As a woman ages, her supply of eggs decreases. Menopause occurs naturally after a woman's ovaries fail to function and menstruation ends completely. (Menopause may also be induced if the ovaries are surgically removed.)

Perimenopause. Menopause does not occur suddenly. A period called perimenopause usually begins a few years before the last menstrual cycle. There are two stages in the transition:

• Early Stage. Perimenopause can begin in some women in their 30s, but most often it starts in women ages 40 - 44. It is marked by changes in menstrual flow and in the length of the cycle. There may be sudden surges in estrogen.
• Late Stage. The late stages of perimenopause usually occur when a woman is in her late 40s or early 50s. In the late stages of the menopausal transition, women begin missing the periods until they finally stop. About 6 months before menopause, estrogen levels drop significantly. The fall in estrogen triggers the typical symptoms of vaginal dryness and hot flashes (which can last from half a year to more than 5 years after onset of menopause).

Menopause. Menopause is considered to have occurred when a woman has gone a full 12 months without a period. At the point at which menopause occurs, the following hormonal changes occur:

• Ovarian secretion of estrogen and progesterone ends.
• Once the ovaries have stopped producing estrogens, however, they still continue to produce small amounts of the male hormone testosterone, which can be converted to estrogen (estradiol) in body fat.
• In addition, the adrenal gland continues to produce androstenedione (a male hormone), which is converted to estrone and estradiol in the body fat.

Click the icon to see an image of the adrenal glands.

• The total estrogen produced after menopause is, however, far less than that produced during a woman's reproductive years.

The average age that women reach menopause is 51 years although it can occur as early as age 40 to as late as the early 60s. Women now have a life expectancy of more than 80 years. Currently, women can expect to live some 30 or 40 years of their life in the postmenopausal state.

Menopause is not a disease. However, many conditions are associated with estrogen depletion, including heart disease, osteoporosis, and other complications. Fortunately, effective treatments are available for these conditions.

In a number of studies, most women have reported menopause as a positive experience and have welcomed it as a sign of a new stage in life.

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Review Date: 07/26/2010
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)