||Scientists from America claim that women who take a male sex hormone to boost their sex drive in middle age could be increasing their risk of breast cancer.
They found that hormone replacement therapy that combines testosterone and oestrogen can more than double a woman's chances of having the disease.
Although testosterone is normally associated with men, it also drives libido in women.
Their study enrolled more than 120,000 nurses, of whom 4,610 developed breast cancer over 24 years.
Just 29 were taking oestrogen plus testosterone, but they had a 77 per cent higher risk of developing breast cancer than those who had never used hormone therapy.
The findings, published in the Archives of Internal Medicine, say: "Although menopausal therapies may provide improvement to sexual functioning, general wellbeing and bone health, the increased risk of breast cancer may outweigh these benefits”.