Highs and woes of runners' hormones.

Highs and woes of runners' hormones

Runners who train more than 45 mileseach week apparently have chronically elevated amounts of certain stress hormones --and therefore potentially harmful blood hormone profiles that are similar to those seen in patients with depression or anorexia, say scientists.

Researchers in Bethesda, Md., at theNational Institute of Child Health and Human Development (NICHD), the Uniformed Services University of the Health Sciences and the National Institute of Mental Health found that certain runners maintained unusually high blood levels of adrenocorticotropic hormone (ACTH) and cortisol, hormones that help the body adapt to stress. Data came from comparing subjects who did not exercise regularly to two groups of runners: one moderately trained by running 15 to 25 miles per week, the other highly trained at more than 45 miles per week. Blood samples were drawn from the 21 subjects --all men--during treadmill exercise, as well as at other times during the day.

While all three groups had elevatedACTH and cortisol levels during intense exercise, the levels in the highly trained group persisted at roughly 40 percent above those in the other groups. In a report in the May 21 NEW ENGLAND JOURNAL OF MEDICINE, the scientists say the reason for the exercise-dependent, chronic hormone elevation is unclear and may represent either "an adaptive change to the daily stress of strenuous exercise or a marker of a specific personality profile.'

Although the hormonal similarities todepression and anorexia nervosa are intriguing, their significance remains a mystery. "This [study] opened a lot of new questions [about exercise and stress] we hadn't thought of before,' coauthor George P. Chrousos of NICHD said in an interview. "The data will come, but we need more prospective studies where we follow the athletes through training. Until that time, we won't know for sure.' He says a psychological study of 50 "compulsive athletes' is under way.

Whatever the cause, the hormonesinvolved serve multiple functions in the body, and findings from the study may have broad implications, says Chrousos. He says elevated levels could be related to mild suppression of the immune system, because cortisol has been suspected for years of causing immunosuppression. Also, it could explain the reproductive-system problems seen in young athletes--male as well as female-- undergoing endurance training. Moderation, say the authors, may be the best, since what "would be beneficial in the short term may be detrimental . . . over prolonged periods.'