Menopause is the beginning of a new, and often liberating and empowering, phase of life for women. Although it marks the end of cyclic functioning of the ovaries and thus of menstrual periods, it is a natural transition to a phase of life that can last 30 to 40 years, or even longer! After roughly four decades of nurturing and releasing an egg each month (pregnancy excepted), your ovaries call it quits on the reproductive front. Given that the average age of U.S. women at menopause is 51 years, most of us will spend more than one-third of our lives in the postmenopause. Symptoms of the underlying hormonal shifts that lead up to this event may manifest themselves for up to 10 years beforehand.

Perimenopause (the prefix peri- is Greek for “around” or “near”) refers to the interval before menopause when fertility wanes and menstrual cycles become irregular, through the first year after the final menstrual period. Perimenopause varies greatly from one woman to the next. On average, it lasts three to four years, although it can be compressed into just a few months before the final menstrual period or extend as long as a decade. Some women feel buffeted by hot flashes or mood swings and wiped out by heavy periods or insomnia, while others have no bothersome symptoms. Menstrual periods may cease rather abruptly or continue erratically for years.

For someone planning a pregnancy, confronting her declining fertility can be a major issue. Even for those who do not wish to become pregnant, harbingers of menopause such as hot flashes and fluctuating periods that occur well before the actual event can be bewildering. To demystify what is happening to you, let’s take a look at the midlife hormonal changes that underlie your symptoms.

What’s Happening to My Body? Understanding Hormonal Changes
Hormones are chemicals that are produced and released into the bloodstream by a variety of specialized endocrine glands and by a region of the brain called the hypothalamus. (Listed in order from head to toe, these glands are the pineal and pituitary glands near the brain, the thyroid gland in the neck, the adrenal gland and the pancreas in the midsection, and, further down, the ovary [in women] and testes [in men]. Other select cells throughout the body, such as those in the fat tissue, also have the ability to make hormones.)

The word hormone, derived from the Greek word for “messenger,” is a fitting name. Hormones travel to cells and tissues throughout the body, exerting a powerful influence on our health, feelings, and behaviors. During the menopausal transition, the starring hormone is the estrogen produced-or, as we will see, not reliably produced-by the ovaries. To understand estrogen’s importance, we first need to back up and examine its role in reproduction-and health-earlier in life.

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By Manson, JoAnn E. and Bassuk, Shari S.
Hot Flashes, Hormones, and Your Health

JoAnn E. Manson, M.D., is a professor of medicine and the Elizabeth F. Brigham Professor of Women’s Health at Harvard Medical School, Chief of Preventive Medicine at Brigham and Women’s Hospital, and codirector of the Connors Center for Women’s Health and Gender Biology. The only person to have served as a lead investigator on two of the most influential studies of women’s health ever conducted-the Women’s Health Initiative and the Harvard Nurses’ Health Study-Dr. Manson is widely recognized as one of the world’s leading authorities on women’s health.

Shari S. Bassuk, Sc.D., is an epidemiologist and science writer at Brigham and Women’s Hospital in Boston who frequently collaborates with Dr. Manson.