What happens during menopause? Science is finally piecing it together.

Every woman who lives to midlife eventually goes through the hormonal transition that is menopause. Yet this significant biological event has long been shrouded in secrecy, spoken of in hushed terms or referenced with euphemisms like “the change.” Only in recent years has menopause been discussed more openly among women and the media, says Nanette Santoro, chair of obstetrics and gynecology at the University of Colorado School of Medicine and a longtime menopause researcher.

Much of what is known about menopause comes from the Study of Women’s Health Across the Nation (SWAN), an epidemiological investigation that has followed some 3,000 women in the United States since 1994. It’s a good start, but more, much larger cohort studies are needed to answer the many questions that remain, Santoro says. (By contrast, the famed Framingham Heart Study has tracked more than 14,000 individuals.) It was SWAN, for example, that found women with frequent, persistent hot flashes are at increased risk for cardiovascular disease. And it was SWAN that confirmed women’s longstanding observations that the body’s lean mass declines and its fat increases during the transition, even if overall weight does not change.

Other research has led to a better understanding of the biology behind menopause’s marquee symptom: the hot flash. Researchers from the University of Arizona, the University of North Carolina and elsewhere have discovered that declining estrogen in the brain’s hypothalamus causes certain neurons to enlarge, which agitates sections of this brain region involved with temperature regulation. This important discovery is expected to lead to new, non-hormonal, targeted therapies. (Read more in Is It Possible to Cure Hot Flashes? We May Be Getting Closer.)

So what exactly triggers menopause?

It all begins with perimenopause.

A baby girl is born with every egg cell inside her ovaries that she will need during her lifetime. Surrounding these eggs are granulosa cells that produce hormones, most notably estrogen. In midlife, as egg cells become less numerous and less viable, estrogen production declines.

This, combined with less frequent egg releases, leads to irregular menstrual cycles. When several cycles are a week or more late over several months, the woman is said to enter perimenopause.

This stage typically begins in the mid-forties, although a decade earlier or later is normal, and it lasts from between two and eight years. (Late-stage perimenopause occurs when some cycles are delayed at least 60 days.) It is the shifting hormone levels, rather than an absolute drop, that cause the symptoms associated with menopause, Santoro says.

Fertility declines during this stage, although ovulation—and pregnancy—are still possible, according to the North American Menopause Society, which is why the group recommends continued contraception use.

What is menopause?

While many women label the entire process as menopause, that term technically denotes the moment when estrogen levels have dropped so low that ovulation and menstruation permanently cease.

Some doctors measure levels of a hormone, follicle stimulating hormone (FSH)—which ramps up as ovulation lessens—to determine if a woman is in menopause. But since levels fluctuate this is not an accurate marker, says Jackie Thielen, director of the Women’s Health Specialty Clinic at the Mayo Clinic.

In the U.S., the average age for women reaching menopause is 52, although anywhere from the forties to sixties is considered normal. After this point, and for the remainder of their lives, women are in the postmenopause stage.

Can menopause occur early?

A small number of women naturally go through menopause before age 40, which is considered “premature.”

Others who undergo medical treatments that remove or severely damage both ovaries, such as cancer surgery, chemotherapy, and radiation, immediately become menopausal. Because of their abrupt hormone shifts, symptoms from induced menopause are generally more severe, according to NAMS.

What are common menopause symptoms?

Hot flashes: Up to 80 percent of women experience these vasomotor symptoms (VMS), when a sudden, intense sensation of heat rises in the upper body while widening blood vessels bring a flush to the skin.

Flashes generally last from one to five minutes and can occur multiple times a day, according to NAMS. Those happening during the night that are accompanied by profuse perspiration are called night sweats. Flashes may end once a woman reaches menopause, but they can also continue for a decade or longer.

Some women are barely bothered by hot flashes, while others find them stop-in-your-tracks debilitating. “These symptoms are not trivial. They’re impacting many women’s lives, relationships, and ability to function at work,” says Stephanie Faubion, director of the Mayo Clinic Center for Women’s Health and medical director of NAMS.

Sleep problems: Shifting levels of the reproductive hormone progesterone can impede the ability to fall and stay asleep, according to the U.S. Department of Health and Human Services’ Office of Women’s Health. Night sweats also make sleeping a challenge.

Mood changes: Rates of depression in women during perimenopause or menopause are nearly double those not yet in this stage, research has shown.

Whether this is due directly to hormones or to sadness over fertility loss or other issues is unclear. Women who can’t sleep due to flashes and sweats are also more likely to become depressed, researchers have found.

Others who are not depressed may feel irritable or have unexplained crying spells. Those who experienced similar mood swings earlier, around their monthly menstrual cycle or after giving birth, are especially prone.

Vaginal changes: Pain and soreness during intercourse result from tissue thinned as estrogen decreases. Along with similar dryness in the bladder and urethra, this is known as the genitourinary syndrome of menopause (GSM). Most symptoms of menopause eventually resolve, but GSM brings lasting physiological changes, Santoro notes.

When do symptoms strike?

The majority of symptoms appear or ramp up during the late stage of perimenopause, the SWAN study found. But they can also strike early, even before a single period shifts, according to results from an online survey published in 2021. “That study validated so many women’s sense that something is happening even though they are still menstruating regularly,” says Faubion, who was not involved with the research.

What are effective treatments?

Basic lifestyle changes help many women cope. Hot flashes are better tolerated by dressing in layers and by taking slow deep breaths and sipping cold water as soon as one begins. Since higher body fat is linked to worsened flashes, people who are overweight or obese may benefit from dropping weight. Smoking is also linked to hot flash intensity.

Improving sleep requires following a regular schedule, shunning late afternoon naps, and avoiding caffeine and alcohol late in the day.

Several mind-body methods have been proven effective, including hypnotherapy, which diminishes severe flashes significantly and cognitive behavioral therapy (CBT), which reduces their frequency.

Multiple studies have shown that herbs and other remedies touted for menopause relief are “unlikely to alleviate hot flashes,” according to NAMS.

Symptoms that severely impact a woman’s life require medical treatment, especially the hormones estrogen and progesterone. Women who are still perimenopausal are prescribed birth control, because they need higher levels of the hormones to also prevent pregnancy. Women past menopause are prescribed menopausal hormone therapy (MHT), typically in patches or pills, NAMS’ Faubion says.

Many doctors are afraid to prescribe menopausal hormone therapy because of widely publicized results in 2002 from the Women’s Health Initiative that found increased risks of heart disease, breast cancer, and stroke, for women taking estrogen and progesterone, especially well past menopause, Faubion says. But that study wasn’t designed to determine if younger women in the throes of symptoms benefit from the treatment, and only a small percentage of them were included, she notes. Subsequent reevaluations of the WHI findings have rejected their conclusion that MHT is not safe for this group, she says.

“If a woman is under 60 and within 10 years of menopause onset, the benefits of hormone therapy tend to outweigh the risks,” Faubion says. That may not be the case for those with a history of breast cancer, uterine cancer, liver disease, heart disease, stroke, blood clots, or cigarette smoking, who should have a frank discussion with their doctor.

Other drugs prescribed for menopause that have shown some benefit include clonidine (a drug used to treat hypertension) and gabapentin. With the discovery of the brain neurons as a cause of hot flashes, a targeted, non-hormonal treatment, fezolinetant, is currently being reviewed by the U.S. Food and Drug Administration. In initial research, the drug reduced weekly flashes by 45 percent.

GSM symptoms may be treated with a vaginal moisturizer or with estrogen administered vaginally, which seems to be safer than systemic hormones, Mayo’s Thielen says. Pelvic floor physical therapy and vaginal laser treatments (to stimulate blood flow) are also worthwhile, according to MyMenoPlan, a website aiming to personalize treatment advice that was developed by a network of menopause researchers and funded by the National Institutes of Health.

Since menopause symptoms can last for years, effective coping also involves embracing a new normal, Thielen says. “The process of losing estrogen and learning to live with erratic and then low levels is what the menopause experience is all about.”