Women who take medications for diabetes should pay closer attention to their breasts, as Danish researchers have found that diabetic medications appear to affect women's breast density in different ways.
The team, headed by Zorana Andersen, an epidemiology professor at the University of Southern Denmark, looked at the mammograms of 5,644 women who had an average age of 56. The mammograms were taken from 1993 to 2001, and the women were a part of the Danish Diet, Cancer and Health study.
When the team compared breast density in the participants, they found that women who used insulin injections were two times more likely to have breasts that were either dense or mixed, meaning they were dense and fatty. This association remained significant even after the researchers factored in variables such as body mass index and menopause.
"Insulin is a growth promoting factor of all body tissues," Andersen said. "Thus it is plausible that it can increase the amount of epithelial or stromal tissue in the breast, thus increasing overall breast density."
Women who took metformin, which is an oral medication, however, had less density in their breasts. Overall, the researchers found that diabetic women in general were not very likely to have dense or mixed breasts.
The researchers noted that while studies have found that women with denser breasts have a higher risk of breast cancer, their findings are not suggesting that insulin increases breast cancer risk.
"Our study looked solely at the effect of insulin on breast density. Now we would like to extend our research by following up these women for breast cancer and observing the effect of different diabetes treatments on breast cancer risk," Andersen said. "If we find a relationship, we need to examine whether a high MD [mammographic density] is responsible, or whether other factors are involved."
"There has been much research into the role of the insulin pathway in breast cancer, but the exact mechanisms are still unknown. This study shows clearly that a link between diabetes treatment and breast density, an important risk factor for the disease, has been made," Fatima Cardoso, Director of the Breast Unit of the Champalimaud Clinical Center in Portugal, said. "I hope that these findings will lead to further research into the effect of cheap, easily-available drugs such as metformin, not just on breast density, but on breast cancer risk overall."
The researchers presented the findings at the European Breast Cancer Conference held in the Netherlands.
