Around 15 per cent of all couples experience infertility, and in about half of these cases it is due to male infertility.
Men with poor semen quality have been shown to have a decreased life expectancy, but the causes are unknown and no biochemical markers or prevention strategies have been developed.
Researchers from Skane University Hospital and Lund University in Sweden have measured the levels of sex hormones and other biochemical parameters in infertile men, and have shown that many of them are at risk of hypogonadism (low levels of sex hormones) as well as signs of metabolic disease and osteoporosis.
They found that one-third of men under 50 with fertility problems, had biochemical signs of low sex hormone levels (eg low testosterone), which is known as hypogonadism. This was 7 times as common as amongst controls.
These men also had low bone density - especially in men with low testosterone - leaving them at increased risk of fractures and osteoporosis.
"We found that a significant proportion of men from infertile couples show biochemical signs of hypogonadism," said Aleksander Giwercman, from Skane University Hospital.
"This may be affecting their fertility, but they can also serve as early warning signs for metabolic diseases in later life, such as osteoporosis or diabetes," Giwercman said.
"We would recommend that levels of reproductive hormones should be checked in all men seeking advice for fertility problems," he said.
The study was published in the journal Clinical Endocrinology.