Running Woe

Female joggers and infertility

The list of joggers' ailments runs on and on. First there were the workaday shin splints and stress fractures. Then, somewhat more exotic, the threat of jogger's nipple and jogger's kidney. In winter, male marathoners have been known to run into penile frostbite. And women runners, it now appears, may face a problem of their own, jogger's infertility, which turns out to be easily reversible if they just stay off their feet.

In a letter to the New England Journal of Medicine, Dublin Gynecologist Colm O'Herlihy notes the case of two women in their mid-20s who regularly ran about 20 miles a week. Both had stopped taking birth-control pills a year ago, and neither had menstruated since. O'Herlihy prescribed high doses of the fertility drug clomiphene citrate but without result. Finally, he asked his patients to lay off the trackwork. Within eight weeks, both had ovulated while taking half the original doses of clomiphene. Shortly thereafter both became pregnant.

The explanation, suggests O'Herlihy, may lie in the leanness of the women. Studies of female ballet dancers have shown that when the level of fat in the body drops below 22% (as opposed to 26-28% for the average 25-year-old), menstruation may cease. In the case of adolescents, body fat levels of less than 17% will delay the onset of puberty. In runners, the incidence of the problem appears to be proportional to weekly mileage. Generally, the effect is reversible with weight gain.

The link between ovulation and exercise may also involve a natural opium-like substance, beta-endorphin, that pours into the bloodstream during stressful workouts. Beta-endorphin has been shown to suppress female hormones regulating the menstrual cycle. In any case, for women runners being treated for infertility, good advice seems to be: stop running.

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