NEW YORK, June 25 (UPI) -- In addition to stimulating the growth of breast cancer, the combination of hormones used in a postmenopausal hormone therapy makes tumors harder to detect.
This can lead to dangerous delays in diagnosis, researchers report in The Journal of the American Medical Association.
The new results deal with a widely used type of hormone therapy that combines estrogen and progestin; the most popular brand is Prempro, made by Wyeth, The New York Times reports.
Women who take the combination are more likely to have changes in their breast tissue that lead to abnormal mammograms, as soon as the first year of use.
This raises questions about the safety of even short-term use, commonly recommended for severe hot flashes and other menopausal symptoms.
The results do not apply to the use of estrogen alone. A second study published in the journal found estrogen alone did not increase the risk of breast cancer.
