Breast cancer in men is rare, but a new study finds that those who have higher estrogen levels are at higher risk of the disease.

Breast cancer is far more rare in men than it is women.

About 2,350 men in the United States will develop the disease this year and 440 will die of it. Age is the main risk factor, with most cases developing in men after age 60.

Although estrogen is known as a female hormone, all men have some of it in their blood.   Cancer Research UK found that men with the high levels of estrogen were two and a half times more likely to develop breast cancer.

Estrogen is known to drive the development of some forms of breast cancer in women, but this was the first time a link between the hormone and the disease in men has been found, the study’s authors said.

High levels of estrogen are often found in men who are overweight or obese, the scientists said. The study appears in the Journal of Clinical Oncology.