<strong>By the faculty

of Harvard Medical School</strong>

<strong>Q: Are "bioidentical" hormones the same as "natural" hormones? And are they safe and effective for treating menopause symptoms?</strong>

A: Many women are confused about the hormonal options for treating menopause symptoms. In 2002, the Women's Health Initiative (WHI) reported that taking Prempro (a combination of estrogen and progestin) causes a small increase in the risk of breast cancer, heart disease and other serious illnesses. As a result, many women stopped taking hormones. But faced with a return of hot flashes, night sweats and vaginal dryness, some sought new alternatives. They include so-called natural and bioidentical hormones.

You might assume that "natural" hormones would be better or safer, but that's not necessarily true. Technically, any product whose main ingredient has an animal, plant or mineral source is natural. The material can be ground, put into capsules and sold over the counter. But it can also be extracted in a laboratory, made by a drug company and sold only by prescription. For example, the soy plant is the source of over-the-counter supplements that some women take to ease menopause symptoms. It's also used, along with yams, to make the estrogen in the Food and Drug Administration-approved hormone prescription drug Estrace.

But unlike Estrace, soy supplements aren't regulated. Since they haven't been as carefully tested in humans, we don't know whether they're actually safe. For example, there is some evidence that certain soy components may stimulate breast-tumor growth. So "natural" doesn't automatically equal "safe."

Bioidentical hormone therapy is often called "natural hormone therapy." That's because bioidentical hormones have the exact same chemical structure as the hormones women make in their bodies. They act the same way in the body, too. And they are made from natural sources (yams and soy). Bioidentical estrogens include 17 beta-estradiol, estrone and estriol. Bioidentical progesterone is simply progesterone.

However, nonbioidentical hormones also come from natural sources. For example, the estrogens in prescription-only Premarin and Prempro are made from pregnant mares' urine, which is natural. But those estrogens are bioidentical for horses, not humans. Likewise, the hormones in another product, Cenestin, are made from plants. But they are not bioidentical.

Bioidentical estrogens and progesterone are used to make a variety of products. Many are FDA-approved and available with a prescription at your local drugstore. Bioidentical estradiol comes in several forms, including pill, patch, cream and various vaginal preparations (see box). Progesterone comes in a capsule or as a vaginal gel.

Are bioidenticals safe? No one knows. Studies have shown they can help relieve hot flashes and vaginal dryness. But few large studies have looked at the differences among the various hormones and different forms. We need more research to understand these differences and compare the risks and benefits.

Women who have a uterus and are taking bioidentical estrogen must still take FDA-approved progestin or progesterone to prevent uterine cancer. But make sure you take the right form in the correct dose. Natural progesterone creams sold over the counter contain too little of the hormone to be effective. And yam-extract creams don't help because your body cannot convert them into progesterone.

Another potentially confusing term is "compounded," which refers to a special mixing process done by pharmacists. Some people mistakenly think that bioidentical hormones must be compounded. But that's not true. Compounding is necessary only when a clinician wants to prescribe hormones in combinations, doses or preparations (such as lozenges or suppositories) that are not routinely available. Because compounded drugs are mixed to order, there are no tests of their safety, effectiveness or dosing consistency. And there is no proof that they have fewer side effects or are more effective than FDA-approved hormone preparations.

This doesn't mean that you shouldn't consider compounded hormones. Just realize that you're going to be an experiment of one. Unless your clinician has a great deal of experience with bioidentical hormones and a particular compounding pharmacy, you're better off with a prescription for commercially available hormones.

It's also worth remembering that, like it or not, menopause itself is all natural! Many women get over menopausal symptoms with time alone. But if your symptoms are bothersome, discuss your options with a physician or other specialist in menopausal health. In addition to hormonal treatments, there are other, nonhormonal alternatives, which we'll cover in a future column.