Fears about commercial hormones have led a growing number of women to try customized cocktails of plant hormones to relieve menopause symptoms.

These are mixtures of estrogens and progesterone that are extracted from plants but have the same molecular structure as the hormones produced by the human body. In fact, they are often referred to as bio-identical hormones.

But as the custom-mixed hormones grow in popularity, they are starting to come under increased scrutiny. Drug maker Wyeth, the biggest seller of prescription hormones, this month called on the Food and Drug Administration to investigate the sale and marketing of these compounded bio-identical hormones. A lawsuit filed by a group of compounding pharmacies -- which mix the hormones -- is seeking protection against FDA actions, and likely will be heard next year.

At issue are claims by compounding pharmacies that the bio-identical hormones are better or safer than the branded hormone products sold by drug makers. The FDA has said doctors and patients should assume all hormones carry similar risks and benefits. But some doctors and pharmacy companies advocate custom-mixed bio-identical hormones, saying they are likely safer and more effective because they are a chemical match to a woman's natural hormones and can be tailored to her specific needs.

For years compounding pharmacists have created custom mixes of drugs for patients who for some reason can't use a commercially manufactured drug. A patient may be allergic to an ingredient, or may need an unusual dose or a different form of a drug -- such as a cream or a liquid -- than what is available through commercial drug firms.

Although hormone compounding has been widespread in Europe for years, interest in the U.S. is surging. In recent years, compounding has grown in popularity as women seek alternatives to menopause hormones after a major U.S. study of Wyeth's Prempro showed high risk for heart problems and breast cancer among older women taking the drugs.

As many as two million women in the U.S. use customized hormones for menopause symptoms, according to some pharmacies, including customdrugs.com, the Web site for South River Compounding Pharmacy of Midlothian, Va. Typically, proponents of bio-identical hormones use saliva tests to measure hormone levels and adjust the dose accordingly. Critics say such tests are unreliable.

There's no scientific research to back up the theory that bio-identical hormones carry fewer risks than hormones made by drug companies. Advocates say common sense should tell us that they are a better option -- and argue that concerns about the lack of controlled studies are raised by turf-protecting drug companies.

"Nobody ever did a double-blind study to see if we need water on grass -- we just know that," says Steven F. Hotze, founder of the Hotze Health and Wellness Center in Houston and owner of a compounding pharmacy that is leading the legal fight against the FDA. "We know they work because our patients get well. That is a scientific experiment of one, and it works over and over again."

Pharmacy firms say the cost of bio-identical hormones are comparable to or slightly higher than the price of drug makers' hormones, and many, but not all, insurance plans cover the cost.

The top-selling hormone, Prempro, is a mix of estrogens derived from mare urine and progestin called medroxyprogesterone acetate, or MPA. But some bio-identical hormones also are sold by drug companies. Warner Chilcott's Estrace and Berlex's Climara patch contain estradiol, a plant-derived estrogen chemically similar to the estradiol produced by the body. Solvay's Prometrium is a bio-identical progesterone that is also chemically similar to a woman's natural progesterone.

Doctors who use compounding pharmacies say that bio-identical hormones mass-produced by drug companies aren't right for many women who require tailored doses. "I want to be able to adjust it because I want to give you as little estrogen as necessary, but I want to give you enough to feel OK," says Dr. Hotze. "I can't do that with the one-size-fits-all treatments that the drug companies have."

Pharmacies are regulated by state laws, so compounding-pharmacy companies say the FDA doesn't have jurisdiction over their actions. But drug makers say U.S. compounding pharmacies are now mass-producing hormones for women -- essentially acting like drug manufacturers -- and so should be subject to the same rules and scrutiny of the FDA.

Other doctors have raised concerns that the lack of federal oversight of the practices of compounding pharmacies puts consumers at risk. One government survey of 29 products sampled from compounding pharmacies, including some hormones, found that more than a third of the samples failed one or more standard quality tests, including some tests showing the drugs were less potent than promised.

In seeking FDA action, Wyeth says it isn't complaining about the legitimate practices of compounding pharmacists. But it says many now make unsubstantiated marketing claims and that women are confused about the real risks and benefits of bio-identical hormones. The complaint doesn't ask the FDA to investigate a specific pharmacy but to look into what Wyeth claims are illegal practices throughout the industry.

"The line is blurred and that's why people are confused," says Ginger Constantine, vice president of women's health at Wyeth. "As a physician I have concerns on a patient level -- people need full disclosure of what they're getting."