Infertile men may be twice as likely to develop breast cancer than those who have no difficulty fathering children, a study has suggested.
Male fertility hormones could be a factor, scientists said, and their research may provide insights into the “underlying causes of male, and possibly even female, breast cancer”.
About 370 men are diagnosed with breast cancer each year in the UK. Because it is rare, research is usually limited to a small number of patients.
But a new study by charity Breast Cancer Now looked at 1,998 men newly diagnosed with the disease in England and Wales over a 12-year period.
The participants were asked whether they had biological children, if they or their partners had ever experienced problems conceiving or if they had visited a doctor or clinic over fertility concerns.
Researchers then compared the fertility of the men with breast cancer to 1,597 men with no history of the disease.
Although the biological reason remains unclear, they found that men diagnosed with breast cancer were more likely to report fertility issues.
“These are important findings,” said study author Dr Michael Jones, who specialises in genetics and epidemiology at the Institute of Cancer Research.
“Our study suggests that infertile men may be twice as likely as those without fertility issues to develop breast cancer.
“The reasons behind this association are unclear, and there is a need to investigate the fundamental role of male fertility hormones on the risk of breast cancer in men.”
He added: “We hope this could lead to insights into the underlying causes of male, and possibly even female, breast cancer.”
Dr Simon Vincent, from Breast Cancer Now, said he hoped the knowledge gained from the study reaches men “who might benefit from being aware of male breast cancer”.
The findings are published in Breast Cancer Research.