Endocrine Abstracts

Objectives: Mountain biking has become increasingly popular worldwide. Mountain bikes, are a common source of significant injuries including chronic overuse injuries affecting the genitourinary tract. Erectile dysfunction and infertility are some of the reported urogenital problems in male riders. Our aim was to evaluate the testicular function in male mountain bikers.

Methods: Thirty male professional mountain bikers with a mean age of 23.4±2.5 years (range, 19–27) and mean body mass index (BMI) of 23.2±1.6 kg/m² (range, 19.5–25.7) were recruited to the study. Twenty-two non-biker healthy male controls with a mean age of 25.5±6.1 years (range, 17–45) and a mean BMI of 22.3±2.0 kg/m² (range, 19–29) were also included in the study. In the study group, the minimum duration cycled was at least one year for each cyclist. None of the cyclists had a history of biking related head or urogenital trauma that required treatment. Fasting blood samples were obtained from all study participants for the measurement of glucose, insulin, leptin, total testosterone (TT), free testosterone (FT), sex-hormone binding globulin (SHBG), leutinizing hormone (LH) and follicle-stimulating hormone (FSH). FT (calculated FT- cFT) and bioavailable testosterone (bioT) were calculated from SHBG and TT using the method of Vermeulen. The presence of insulin resistance was investigated by using the homeostasis model assessment (HOMA) score in both groups.

Results: The study and control groups were comparable in terms of age and BMI. Basal hormonal levels including insulin, leptin, LH, FSH, SHBG, TT, glucose and HOMA scores were similar between the groups. However, bioT, cFT and FT levels were significantly lower (P<0.05) in the mountain bikers than those in controls. Despite the lower mean testosterone levels in the study group, the levels of LH and FSH were within normal range in all cyclists.

Conclusion: The study indicates that professional male mountain bikers have lower testosterone concentrations with no accompanying significant increase or decrease in the concentrations of FSH and LH. Low testosterone levels may be both testicular and extratesticular in origin.