There’s a lot to appreciate about hormones. They play a huge role in everything from getting pregnant to feeling happy to sleeping soundly. Unless, that is, your levels fluctuate―which, for better or worse, is a natural part of growing older. To shed a little light on these changes, it’s first important to understand how your primary hormones work.

Progesterone, which is produced by the ovaries and the adrenal glands after ovulation, maintains healthy cell growth in the uterus. Estrogen is created by the ovaries, the adrenal glands, and fat cells and prepares the uterus to accept a fertilized egg each month. Testosterone is made by the ovaries and the adrenal glands and regulates sex drive. And thyroid hormones (that’s right, produced by the thyroid) control metabolism.

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Read on to learn how all of them impact you at different stages of your life―and what you can do to manage hormonal changes and feel good every step of the way.

In Your 20s and 30s
What’s Happening
These are your peak fertility years, and your menstrual cycle is probably pretty regular.

“Hormone levels go through dramatic changes during your menstrual cycle,” Mary Jane Minkin, a clinical professor of obstetrics and gynecology at the Yale University School of Medicine, said.

A surge in estradiol (a form of estrogen) about 10 days after the onset of your period, right around ovulation, induces a happy mood, while a boost in progesterone in the second half of your cycle can make you irritable.

You Might Notice
A dip in your sex drive if you use a hormonal contraceptive, like the Pill or a vaginal ring.

“These contain synthetic estrogen, which blocks testosterone,” Bat Sheva Marcus, the clinical director of the Medical Center for Female Sexuality, in New York City, said.

The good news? A new contraceptive pill that contains natural hormones (and so may keep your libido intact) is under review by the Food and Drug Administration. (It’s available in Europe as Qlaira.)

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A drop in your fertility
as you enter your late 30s. If you are under 35 and trying to get pregnant and don’t conceive within a year, see a reproductive endocrinologist to check for hormone-related fertility problems. If you’re over 35, give yourself six months.

How to Feel Better
Studies have shown that eating cruciferous vegetables, like broccoli and cauliflower, can help keep estrogen and progesterone levels at the proper ratio, Eva Cwynar, an endocrinologist in Beverly Hills, said. Yams and flaxseed oil may also be beneficial. To help curb severe PMS crankiness, Minkin suggests taking 1,200 milligrams of calcium a day, divided into three doses.

In Your 40s
What’s Happening
You still have regular periods, but your ovaries have begun to produce less estrogen (so you ovulate less effectively) and less progesterone; your estrogen-progesterone ratio shifts (normally, the two balance each other), and testosterone decreases. In other words, you’re entering perimenopause (or pre-menopause), a precursor to menopause that can last up to five years.

“It isn’t a smooth process,” says Minkin.

You may start to experience hot flashes, a lag in your sex drive, and vaginal dryness. Luckily, these symptoms come and go. However, your fertility continues to decline, so it’s a good idea to see your gynecologist for basic testing if you’re trying to conceive.

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You Might Notice
Weight gain. “Thyroid hormones are the key determinants of your metabolism,” Kent Holtorf, an endocrinologist in Los Angeles, said.

Many women produce less of this hormone with age, which causes pounds to creep on. A blood test can determine any deficiencies, and taking thyroid hormones may help normalize your weight.

Sleep problems.
You may have blissfully slept a full eight hours in years past, but the progesterone dip can cause insomnia.

“You may start waking in the middle of the night or have difficulty falling asleep,” Erika Schwartz, an internist and a hormone specialist in New York City, said. “Before turning to a sleep aid like Ambien, get your hormone levels checked. You may need hormone supplementation.”

How to Feel Better
Since this is the first decade in which you’ll experience a natural drop in hormones, you have a few options for recalibrating. The jury is still out on whether supplementing with soy, which has a weak estrogenic effect in the body, is wise, since some studies have linked it to breast cancer. 

However, a study published last year in the Journal of the American Medical Association concluded that when consumed at moderate levels, soy doesn’t contribute to a higher risk of death or a recurrence of the disease in breast cancer survivors. To play it safe, experts suggest eating soy foods―like soy milk, miso, edamame, and tofu―rather than taking supplements.

If you have occasional hot flashes, taking 400 international units of vitamin E daily can help alleviate them, according to a study from Tarbiat Modarres University, in Iran. To help combat regular or severe hot flashes, consider taking a low-dose birth control pill, which contains small amounts of estrogen plus progestin, a synthetic form of progesterone (brand names include Alesse, Loestrin, and Mircette). Or talk to your doctor about estrogen replacement therapies.

In Your 50s and Beyond
What’s Happening
Progesterone production has slowed considerably, and most of the estrogen that your body makes comes from your adrenal glands and fat tissue, not your ovaries. By age 51, on average, you’ve reached menopause; it’s official when you haven’t had a period in over a year. Odds are, your testosterone levels are erratic, producing more hot flashes and causing your sex drive to zigzag. (Bear in mind, these issues may not feel nearly as unpleasant as they sound.)

You Might Notice

Dry skin. “Estrogen is involved with mechanisms that keep skin moist,” Minkin said, so the natural drop in the hormone means parched skin (and possibly brittle hair and nails) and a need for richer creams and conditioners.

A feeling that your short-term memory is on the fritz.
“Both estrogen and thyroid hormones are needed for optimal brain function,” Holtorf said. “When they drop in menopause, those low levels result in minor memory problems and cognitive dysfunction.”

How to Feel Better
Be proactive.

“It drives me crazy when women say, ‘I’ll just deal with my symptoms, and eventually it will be over,’ ” Minkin said. “Symptoms of menopause should be a wake-up call to see your doctor.”

Hormone replacement therapy (HRT) is considered the gold standard for relieving all those irksome symptoms, including memory loss. But a landmark five-year study published in 2002 by the Women’s Health Initiative suggested that HRT may be related to an increased risk of breast cancer, heart disease, and stroke.

Because of this, “deciding to go on HRT is highly individualized,” said Régine Sitruk-Ware, a reproductive endocrinologist in New York City and the executive director of research and development at the Population Council.

Experts believe you get the most benefits if you start HRT as close to the onset of menopause as possible and stay on it for five years at most, stopping once the hot flashes and the night sweats subside. There are dozens of HRT pills, patches, creams, gels, and injections to choose from, ranging from synthetic hormones to bioidentical ones (which have molecular structures identical to the hormones your body produces).

Some good news:
On the horizon are new HRT pills designed specifically to activate estrogen receptors in the body without causing uncontrolled cellular replication―a.k.a. cancer. What else can you do? Eat foods like salmon, walnuts, and peanuts. They’re rich in essential fatty acids and L-arginine, which safely increase testosterone levels―and may improve your sex drive.