High levels of ‘male’ hormones, or androgens, in young women apparently raise their risk of developing breast cancer, according to new research.

Androgens are normally present in women, albeit at much lower levels than in men. Elevated androgen levels have been linked with breast cancer in studies of postmenopausal women, but it was unclear if this also applied to premenopausal women.

In the current study, in the Journal of the National Cancer Institute, Dr. Rudolf Kaaks, from the International Agency for Research on Cancer in Lyon, France, and colleagues compared androgen levels in 370 premenopausal women who were later diagnosed with breast cancer with levels found in 726 similar women without breast cancer.

The likelihood of developing of breast increased significantly as levels of testosterone and androstenedione rose.

The absolute risks of women younger than 40 years developing breast cancer over a 10-year period ranged from 2.6 percent for those with the highest testosterone levels to 1.5 percent among those with the lowest levels.

The study “provides strong evidence that the risk of breast cancer among premenopausal women is directly related to circulating levels of testosterone and androstenedione,” Kaaks’ team concludes.

Further studies, however, are needed to see if lifestyle changes or other interventions can lower these levels and reduce the cancer risk.

SOURCE: Journal of the National Cancer Institute, May 18, 2005.