In a retrospective case-control study of 2,226 females, researchers found that women with primary hypothyroidism (under-active thyroid) had a 61 percent lower risk of developing invasive breast cancer. Additionally, women newly diagnosed with breast cancer were 57 percent less likely to have the under-active thyroid gland condition compared to a control group of healthy women.
Even more, the breast cancer patients on the study who also had a history of hypothyroidism tended to be older when diagnosed and have a less aggressive, indolent variety of the disease that was sensitive to estrogen treatment.
"These intriguing and very exciting findings suggest a biological role of thyroid hormone in women with breast cancer that could offer some prognostic or therapeutic value, perhaps suggesting novel preventive strategies," says Massimo Cristofanilli, M.D., associate professor in M. D. Anderson's Department of Breast Medical Oncology and the study's lead author. "The study also draws attention to the role of thyroid hormone and its potential interaction with estrogen to promote the onset of breast cancer. We need to consider that while in the past we've looked only at the role of estrogen on breast tissue to promote the onset of cancer - thereby promoting research that brought therapeutic and preventive hormonal approaches to the patient - many more studies need to be done to explore the role of other hormones.
The influence of thyroid gland disease on breast cancer has been debated for some time. Other smaller studies have focused on a population of women with several thyroid conditions, such as hypothyroidism, hyperthyroidism (over-active thyroid), thyr
Contact: Laura Sussman
University of Texas M. D. Anderson Cancer Center