Dr. Wulf Utian, executive director of the North American Menopausal Society, says he has concerns with some of the issues surrounding bioidenticals.

"This is a multibillion-dollar industry," says Dr. Utian, who also is a gynecologist at the world-renowned Cleveland Clinic. "There's no such thing as a natural hormone. They're all made in the lab one way or another."

Dr. Utian cautions women to be wary of any manufacturer making claims of safety that can't be proven. "When a company, whether on its website or in its marketing materials, makes claims of safety that they cannot prove, they are misleading women," he says. "I think that's criminal."

Dr. Northrup agrees that taking any hormones comes with risk and says that no woman should undergo hormone replacement therapy without the supervision and care of a doctor. "You want to be working with a team," she says.