A hormone that boosts growth in kids may lead to breast cancer, and women with high levels are at higher risk, according to a new study by UK scientists.
It is a known fact that cancer is cause by uncontrolled division of cells in the body.
The hormone, IGF-1, stimulates cell division, especially during childhood. It is also being investigated as an anti-ageing treatment.
Information from nearly 5000 women across 12 countries was analysed by Cancer Research UK scientists at the University of Oxford.
The results amongst these women suffering from breast cancer showed that the 20 per cent of women with the highest blood levels of the growth factor were 28 per cent more likely to develop the disease than the 20 per cent with the lowest levels.
Moreover, the effect is more pronounced with a certain type of breast cancer that responds to the female hormone oestrogen.
"Over the last few years there has been increasing interest in the possible link between growth factors and breast cancer, but the results have been inconsistent. Putting together all the information available worldwide gives us conclusive evidence that the higher a woman's blood levels of IGF-I, the higher her risk of breast cancer," the Independent quoted Professor Tim Key, lead author of the study, as saying.
The hormone is being investigated for its role not just in breast cancer, but also prostrate cancer.
This finding has come in the footsteps of the last discovery of five new genetic sites that increase a woman's risk of developing breast cancer by 6 to 16 per cent. They take the total number of common "low-risk" genetic sites associated with breast cancer to 18.
Scientists, however, are still unaware which genes are responsible. But as more of them are identified it may be possible to create tests for a combination that significantly increase risk.
Helen George, head of science information at Cancer Research UK said, "This research takes us a step closer to developing a powerful genetic test for the disease. Such a test could help doctors identify women who have an increased breast cancer risk so that they can make informed decisions about how to take steps to reduce their chance of developing the disease."
The study has been published in the journal Lancet Oncology.