NEW YORK, Oct 27 (Reuters Health) -- Men who participate in endurance training may be just as likely as women to experience a drop in sex hormone levels, although female athletes are much more likely to be studied, according to a North Carolina researcher.
"Not until recently have studies seriously addressed the question of how exercise training affects the male reproductive system," reported Dr. Anthony Hackney in the Encyclopedia of Sports Medicine and Science.
"Research findings in this area have led some investigators to suggest that the effect of exercise training on the male reproductive system may be comparable to some degree to that found in women," he writes.
Some studies, usually of distance runners involved in the sport for 1 to 15 years, have found that male athletes have testosterone levels at 60% to 85% the levels of men the same age who are not involved in endurance training, according to the review of research conducted by Hackney, who is at the University of North Carolina, Chapel Hill.
Some research has found a decrease in testosterone in as little as 1 to 6 months of training, while others found no decrease after 2 to 3 months of training. However, it is not clear if the drop in testosterone is detrimental to health, and in fact, may be beneficial.
"Currently, there is little evidence to suggest that the development of low resting testosterone levels in men doing endurance training has any major detrimental effect on the testosterone-dependent physiological processes of the body," according to the report.
"Some researchers indicate that lowering testosterone may have cardiovascular protective effects and decrease the risk of coronary heart disease," Hackney writes.
A German study found that lowering testosterone with drugs increased blood levels of HDL, or "good" cholesterol, although it is not clear if this occurs in those who exercise their way to lower testosterone levels.
