Estradiol levels predict bone mineral density in male collegiate athletes: A pilot study

Objective Strenuous training commonly results in amenorrhoea, which contributes to bone loss in some female collegiate athletes. However, the impact of athletic training on endocrine function and bone mineral density (BMD) in male collegiate athletes is less well understood. The objective of the study was to investigate the specific endocrine determinants of BMD in male collegiate runners and wrestlers, including the potential impact of gonadal steroid levels. Design Cross-sectional study. Patients Twenty-six division I collegiate male athletes (wrestlers, runners and golfers). Measurements Main outcome measures included (i) BMD endpoints measured by dual energy x-ray absorptiometry (DXA); (ii) endocrine end-points: total and free oestradiol, total and free testosterone; (iii) body composition end-points: lean and fat mass, measured by DXA; and (iv) exercise end-points: maximal oxygen uptake (VO ₂ max), number of miles run weekly and grip strength. Results Free and total oestradiol levels were important positive determinants of BMD. In contrast, total and free testosterone levels were not significant predictors of BMD at any skeletal site (except for free testosterone at the radius). In addition, lean body mass, % ideal body weight, total body weight, body mass index (BMI) and hours per week of resistance training were positive predictors of BMD. VO ₂ max was a negative predictor of BMD. Mean BMD was higher at all skeletal sites in the wrestlers compared with the runners and a comparison group (golfers). Conclusions Our data suggest that oestradiol levels, BMI, and resistance training are more important determinants of BMD in male collegiate athletes than testosterone.