Some doctors in Canada are warning women that they are courting risks they may not even be aware of when they turn to bio-identical hormone replacement therapy to treat the symptoms of menopause.

The therapy, also known as BHRT, uses hormones derived from plants such as yam and soy. BHRT has been growing in popularity because of fears over risks from traditional hormone replacements, derived from the urine of pregnant horses.

The use of standard hormone therapy for women suffering hot flashes, mood swings and other symptoms of menopause plunged after a landmark study in 2002 linked it with an increased risk of breast cancer.

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The use of standard hormone therapy for women suffering hot flashes, mood swings and other symptoms of menopause plunged after a landmark study in 2002 linked it with an increased risk of breast cancer. (iStock photo)

Women using BHRT therapy say they feel more comfortable with bioidenticals because they consider them more natural. The support of celebrities such as actress Suzanne Sommers has also helped fuel its popularity.

"I would never go the traditional hormone replacement. I grew up with natural herbs and that sort of thing," says Rose Niemirowski, who has been using a bio-identical cream for the past five years.

Her Oshawa-based doctor, Dr. Blake Gibb has been offering the treatment for years and says none of his patients have reported problems. In fact, he says he's so busy with bio-identical therapy that he turns down about 10 women a day asking for treatment.

"The evidence is in my practice," he says.

But other doctors are raising flags, warning that unless the hormone estrogen is balanced with progesterone, women could be putting themselves at risk of developing uterine cancer.

"To say it's bio-identical doesn't mean it's safe," Dr. Richard Boroditsky, a professor at the University of Manitoba's department of obstetrics, gynecology and reproductive sciences.

To avoid the risk of uterine cancer most women taking estrogen also need to take progesterone, he says. While most bio-identical therapies use progesterone creams, Dr. Boroditsky says women can't be sure of the levels of hormones they're absorbing.

"We've known this for years - that if woman takes un-opposed estrogen, she increases her risk eight to 10 times over the normal chances of developing cancer of the uterus," he says.

The BHRT creams, which are hand-mixed by pharmacists, are untested and unregulated by Health Canada.

The Canadian Society of Obstetricians and Gynecologists, the North American Menopause Society and the U.S. Food and Drug Administration have all issued statements advising women that these treatments carry the same risks as traditional hormone therapies. They warn that they have not undergone the same rigorous tests for safety and effectiveness.

Winnipeg woman Gail Clisby, who lost her uterus to cancer, says she is living proof there are indeed side effects.

Dr. Boroditsky, who now treats her, told her he believes her cancer might have been caused by a hormone imbalance while using a bio-identical product.

"It wasn't expressed to me how delicate a balance you need to have," says Clisby.