Orlando, Fla. ? Cathy Rentsch has been taking estrogen every day for 25 years, and she has no intention of stopping anytime soon.

Sure, she’s heard about the concerns surrounding the hormone, which just this week was added to the federal government’s list of known human carcinogens. But with all the things that might cause cancer in the world, Rentsch figures the small risk is easily overwhelmed by the benefit.

“I just don’t worry about it at all, not at all,” said Rentsch, 50, a licensed practical nurse who works in an Orlando gynecology/obstetrics practice. “I can’t imagine going without it, and I hope that other women won’t be scared” unnecessarily.

But the latest wrinkle is likely to create more confusion about the hormone, which is widely used in birth control pills and hormone replacement therapy for women dealing with the symptoms of menopause.

The National Institute of Environmental Health Sciences put these estrogen compounds on its 200-plus list of cancer-causing agents, along with 14 other additions, including wood dust and broad-spectrum ultraviolet radiation.

Institute officials say the hormone carries an increased risk of uterine and breast cancers. This comes as no surprise to doctors, who say the official classification of estrogen as a carcinogen is not going to force changes in how they prescribe the medication.

Already last summer, doctors reassessed the use of estrogen when a widely publicized study found that it does not offer protection from heart disease as once thought. But they long have know about the possibility that estrogen contributes to some cancers.

“This is not news to us,” said Dr. Ashley Hill, a Florida Hospital obstetrician and gynecologist. “People need to understand that purpose of this (carcinogen) list is for education, it’s not meant to change practice guidelines.”

The listing only applies to estrogen alone. The NIEHS did not evaluate whether estrogen taken in combination with progesterone is a problem.

“It may not have the same carcinogenic effect, or it may have no carcinogenic effect at all,” said Christopher Portier, director of the Environmental Toxicology Program for the NIEHS. “We didn’t look at that.”

But doctors say studies have shown that using estrogen in combination with progesterone cuts the risk of uterine cancer. And many women take such a combination.

All birth control pills in the United States include both hormones, and most hormone replacement therapy incorporates the two. However, women who have had their uteruses removed take estrogen alone.

Women who have concerns should talk to their doctors, experts say. There is no overarching guideline for everyone — people simply need to evaluate their symptoms and make their own decisions.