Men with index fingers longer than their ring finger are at reduced risk of prostate cancer.
A British Journal of Cancer study found men whose index finger was longer than their ring finger were significantly less likely to develop the disease.
Researchers made the discovery after comparing the hands of 1,500 prostate cancer patients with 3,000 healthy men.
Being exposed to less testosterone before birth results in a longer index finger and may protect against prostate cancer later in life, say researchers at the University of Warwick and the Institute of Cancer Research.
Dr Helen Rippon, head of research at The prostate Cancer Charity, said the research added to growing evidence that the balance of hormones we are exposed to before birth influences our health for the rest of our lives.