Possible Mechanisms for Suppression of Testosterone Concentrations with Long Term Exercise

In female athletes menstrual disturbances have been found in association with lower bone density particularly at trabecular sites.Furthermore, stress fractures seem to be more common in women with amenorrhoea or oligomenorrhoea with a relative risk that is between two to four times greater than that of their eumenorrhoeic counterparts. There are few studies investigating the relation of testosterone levels to bone density and stress fracture risk in young male athletes. A recent case report described the clinical features of a 29-year-old male distance runner who presented with a pelvic stress fracture, greatly decreased bone density and symptomatic hypogonadotropic hypogonadism." Using this case as an index, the authors hypothesised that exercise– induced hypogonadotropic hypogonadism could be identified in male athletes by the presence of one or more specific risk factors which included the presence of sexual dysfunction, a history of fracture, and the initiation of endurance exercise before age 18 Years.

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.