With RealAge, he buys lists of women who have answered a test question by saying they have heavy menstrual bleeding, among other criteria. He chooses the ones in the 37- to 49-year-old age range, then sends them a series of e-mail messages. Several of the messages do not mention NovaSure, they just identify heavy bleeding as a problem  then, he said, the messages suggest NovaSure as a solution.

Image Dr. Mehmet Oz, a regular on The Oprah Winfrey Show, is a RealAge spokesman. Credit... Heidi Gutman/ABC

“We’re trying to get out to those customers right now and let them know that it is an option for them,” said Mr. Williamson, the vice president for sales and marketing for the gynecologic surgical products division of Hologic. “A lot of women don’t know it’s a problem, and that’s the thing. It’s not something they necessarily talk about.”

RealAge acts as the middleman between the drug companies and its members: it sends the e-mail messages from its own address and does not release members’ names or e-mail addresses to drug companies. That is because pharmaceutical advertisers are among “the most heavily regulated industries in the world, and they don’t necessarily want those e-mail addresses  they like that we’re a proxy for their messages,” Mr. Mikulak said.

Its access to health information has made RealAge valuable. Founded in 1999, it was acquired by Hearst Magazines in 2007 for an estimated $60 million to $70 million. Though its sales  and the fees it pays Dr. Oz  are not public, it is profitable, and had about $20 million in revenue when Hearst acquired it.

Annie Tomlin, a 30-year-old Web site editor in San Francisco, is a vegetarian who walks everywhere, one of the healthy consumers that RealAge prides itself on. She first took the test after her mother heard about it on Oprah  scoring seven years younger than her actual age  but did not realize the answers were being used by marketers.

“It bothers me because I’m not a fan of the drug companies, and I don’t enjoy the idea of me giving them any help in marketing their medicine,” she said. “While it’s fantastic that we have certain medicines that help save people’s lives, there are also a lot of medicines that are very, very profitable that are pushed on people who don’t need them.”

Mr. Mikulak said that RealAge protected privacy: it does not give personally identifiable information to the drug companies and the advertisements in e-mail messages are clearly labeled as such. RealAge is “providing value in return for the information,” he said.