The study, undertaken by Oxford University, revealed that pre-menstrual women with high levels of sex hormones such as oestrogen and testosterone were between a fifth and a third more likely to develop breast cancer than women with low levels of the hormones.
Professor Tim Key of the Cancer Epidemiology Unit at the University of Oxford said, “While the link between higher levels of sex hormones and breast cancer is well established in older, postmenopausal women, it’s much less clear what effect hormones have on cancer risk in younger, premenopausal women.
“But from this study we can say there appears to be a link, which has important implications for understanding the biology of breast cancer and for planning future research.”
The study also researched the effect of smoking and alcohol on sex levels. The researchers discovered that women who smoked 15 or more cigarettes a day, or drank two or more glasses of wine a day, had higher levels of the male sex hormones compared with women who didn’t smoke or didn’t drink.
Data on hormone levels in the blood of 760 premenopausal women with breast cancer and of 1,700 without was looked at from seven previous scientific studies. The report has been published in The Lancet.
Although 80% of those diagnosed with breast cancer are over fifty, 10,000 women under fifty are diagnosed with the disease every year.
Cancer charities have welcomed the news. Cancer Research UK commented, “With one in five breast cancers now diagnosed in women under 50 it’s important that we find out as much as we can about what increases the risk for younger women. We don’t yet know why having higher levels of some sex hormones might increase a woman’s risk so further research is needed to investigate this link.”
