Males suffering from low semen quality are more liable to be suffering from additional medical problems, especially conditions involving hormones, the circulatory system or diseases of the skin, researchers say.

The quality of semen production seems to be a good indicator of a man's overall health, they say.

"We used a well known marker for overall health," says Dr. Michael Eisenberg, lead author of a study published in the journal Fertility and Sterility. "The less healthy men were, the lower sperm quality overall."

The findings suggest a complete physical examination of men experiencing reproductive issues is a good idea, says Eisenberg, a professor of urology and director of male reproductive medicine at Stanford University.

"About 15 percent of all couples have fertility issues, and in half of those cases the male partner has semen deficiencies," he says. "We should be paying more attention to these millions of men."

In the study, an overall health score was calculated from medical records of more than 9,000 men undergoing fertility evaluations at Stanford from 1994 to 2011.

That score was then correlated to concentrations, volume and the general health of sperm cells observed in their semen samples.

Men who were suffering from hormone, circulatory, skin and urinary conditions were significantly more likely to display semen abnormalities, the researchers found.

In total, 44 percent of the men in the study had some other health issues in addition to the fertility problems that had brought them to the Stanford clinic, issues that could have been a factor in their infertility, Eisenberg and his research team say.

"Given the high incidence of infertility, we need to take a broader view," Eisenberg says. "As we treat men's infertility, we should also assess their overall health.

"That visit to a fertility clinic represents a big opportunity to improve their treatment for other conditions, which we now suspect could actually help resolve the infertility they came in for in the first place."

Previous studies have indicated around one in six men who visit clinics for fertility problems are likely to have some other major medical condition, says Dr. Joseph Alukal, director of Male Reproductive Health at NYU Langone Medical Center in New York City, who was not involved in the Stanford study.

Since men have been found more likely than women to forego annual physical exams, for those men discovered to have semen abnormalities a comprehensive physical exam is worthwhile, he says.

"I think it's just good common sense, Alukal says. "I don't think there's anything that could hurt."