By Helen Briggs
Health reporter, BBC News
Studies on fatherhood and prostate cancer have produced mixed results
Infertile men may have a higher risk of developing prostate cancer, US data suggests.
Researchers looked at the cancer records of men attending infertility clinics in California.
They found men unable to father a child were nearly three times more likely to be diagnosed with prostate cancer than normal.
The authors of the study, published in the journal Cancer, say more work must be done to confirm the possible link.
If confirmed, it might be appropriate for infertile men to be given early prostate cancer screening, they say.
Study leader, Dr Thomas Walsh of the University of Washington in Seattle said: "These are some of the first data to suggest that male reproductive health in early life may be a risk factor for serious malignant disease in later life.
"It is important for investigators and physicians to do further research to find out what might be the common underlying cause that may lead to both infertility and later the development of prostate cancer."
Prostate cancer is the most common cancer in men. Risk factors include age, family history and ethnicity.
SIGNS OF PROSTATE CANCER
Having to rush to the toilet to pass urine
Difficulty in passing urine
Passing urine more often than usual
Pain on passing urine
Blood in the urine or semen
More recently, it has been suggested that fatherhood status might be linked with prostate cancer but studies have shown conflicting results.
The new study looked at the risk of prostate cancer in 22,562 men checked for infertility in 15 clinics in California between 1967 to 1998.
About 4,500 of these men were found to have male infertility - and 19 went on to develop the most aggressive form of prostate cancer.
In a similar sample of men in the general population, 16 men were diagnosed with the high risk form of the disease.
Overall, infertile men were found to be 2.6 times more likely to be diagnosed with the most aggressive form of prostate cancer.
But Dr Helen Rippon, head of research management at The Prostate Cancer Charity, said with such small numbers of men affected, it is difficult to draw any firm conclusions about whether the suggested link does exist.
She said: "This potential new risk factor would need to be backed up by further, large scale studies before any recommendations can be made about targeting early screening for prostate cancer at men with fertility problems."
Ed Yong, head of health evidence and information at Cancer Research UK, said: "It's unlikely that being infertile directly leads to prostate cancer.
"Instead, both infertility and a higher risk of prostate cancer might stem from a common genetic fault, or some aspect of our lifestyle or environment."