They compared concentrations of free testosterone and luteinising hormone in 15 male runners with one or more of the above risk factors and 13 runners with none of the risk factors. Only one of the runners in the first group was identified as having primary hypogonadism and there was no significant difference between groups for hormone concentrations. Bone density, however, was not measured in these runners and correlated with testosterone concentrations. From a clinical perspective, it is important to clarify that although some male athletes do present With reduced testosterone concentrations, these concentrations are generally still within the normal range for adult men. Therefore, detrimental effects on bone density may not be as dramatic as those described for women with athletic amenorrhoea in whom oestradiol concentrations are well below normal.