Prospective evaluation of risk factors for exercise-induced hypogonadism in male runners.

Exercise-induced hypogonadotropic hypogonadism is well recognized among female endurance athletes but is less commonly observed in male endurance athletes. We have reported a well-characterized case of severe acquired hypogonadotropic hypogonadism in a male distance runner with osteopenia, stress fracture, and sexual dysfunction. Using this case as an index, we hypothesized that the presence of 1 or more specific risk factors would prospectively identify male endurance athletes with exercise-induced hypogonadotropic hypogonadism. These include a history of stress fracture, sexual dysfunction, or the initiation of endurance exercise before age 18 years. We studied 28 male endurance runners younger than 50 years who ran more than 40 miles per week. Of these runners, 15 had 1 or more of the above risk factors (group 1), and the remaining 13 had none of the putative risk factors (group 2). A group of 10 sedentary control subjects was also studied (group 3). There was no difference between groups 1 and 2 in weekly training mileage. Group 1 was younger than group 2 (32 +/- 10 years versus 39 +/- 6 years, P < .05) and had a lower body mass index (22.4 +/- 1.9 kg per m2 versus 23.9 +/- 2.2 kg per m2, P < .05). By bioelectric impedance, preliminary data showed that group 1 had a reduced body fat content (group 1, 14.5% +/- 2.8%; group 2, 16.9% +/- 2.0%; and group 3, 17.5% +/- 4.1%; P < .05). Fasting morning concentrations of free testosterone (group 1, 45.3 +/- 26.4 pmol/l; group 2, 88.8 +/- 24.3 pmol/l; and group 3, 69.1 +/- 21.5 pmol/l) and luteinizing hormone (group 1, 1.7 +/- 0.7 IU per liter; group 2, 2.0 +/- 1.1 IU per liter; and group 3, 1.9 +/- 0.6 IU per liter) did not differ among the groups (P > .05). One subject with primary hypogonadism was identified in group 1. The presence of the aforementioned risk factors does not predict the occurrence of exercise-induced hypogonadotropic hypogonadism among male endurance runners in this pilot study. A larger sample size or more discriminating risk factors (or both) may be necessary to identify this uncommon but potentially debilitating condition.