(February 25, 2008 - Insidermedicine) Hormone replacement therapy consisting of both estrogen and progesterone  appears to reduce the usefulness of two common diagnostic tools for breast cancer, according to research published in the Archives of Internal Medicine.

Here are some facts about hormone replacement therapy:

•    Consisting of low doses of one or more female hormones, generally forms of estrogen and progesterone, hormone replacement therapy has long been used to tame the symptoms associated with menopause.

•    Until recently, hormone replacement therapy was also given to women entering menopause because it was believed to reduce the risk of developing certain medical conditions, particularly heart disease.

•    Recent studies have demonstrated that hormone replacement therapy does not have the disease-preventing benefits once associated with it and may even increase the risk of developing some conditions, including breast cancer.

Researchers out of the Los Angeles Biomedical Research Institute at Harbor–UCLA Medical Center studied over 16,000 postmenopausal women who were randomly assigned to one of two groups. The first group of women received hormone replacement therapy consisting of types of estrogen and progesterone while the second group received a placebo. They took this therapy for an average of about five-and-a-half years.

During the treatment period, 199 women taking hormones and only 150 women taking a placebo developed breast cancer. Also, taking the hormones for five years resulted in about one in ten women having an abnormal mammogram finding and about one in 25 having an abnormal breast biopsy finding that they would otherwise not have had. Even though breast cancer was more frequent in women taking hormones, these diagnostic tests for breast cancer were actually less likely to correctly identify the disease in these women.

Based on these findings, the authors conclude that taking combined hormone replacement therapy places menopausal women at increased risk for having abnormal results of mammograms and breast biopsies while actually reducing the ability of these tests to diagnose true breast cancer.

For Insidermedicine in Depth, I'm Dr. Susan Sharma.