Chronic hypoxia: Endocrine system, body composition and semen changes.

Introduction & Objectives Changes in hematological or cardiopulmonary systems after high-altitude expeditions have been well documented in several studies, whereas, to date, controversial reports explored the effects of a prolonged exposure to hypobaric hypoxia on human hormonal profile(s). This study investigated changes of reproductive hormones, body composition and semen analysis, before and after a high-altitude expedition (Manaslu-Himalaya). Material & Methods Seven healthy male mountain trekkers participated to the expedition. Resting levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH), total testosterone (TT), estradiol (E2), prolactin (PRL) and cortisol, were evaluated at sea level (SL), immediately after 43 days of prolonged exposure to hypoxia during a high-altitude trekking (HYPOX) (1300m to 5800m), 10 days after returning at sea level (HYPOX10) and six months after expedition (6MON). Body mass index (BMI), waist circumference, percentage of body fat (%fat), and semen analysis, were also evaluated. Results Compared to SL, FSH and LH were higher at HYPOX (p<0.0002 and p=0.03 respectively) and decreased at HYPOX10, returning to baseline at 6MON. PRL and cortisol showed the same trend of the two gonadotropins. E2 showed lower levels at HYPOX (p=0.001) compared to SL and progressively increased returning to baseline level at 6MON. TT level was unchanged at HYPOX compared to SL, while levels were higher at HYPOX10 (p<0.0002), and returned to baseline at 6MON. BMI, waist circumference and %fat were reduced (p=0.04, p=0.01, p=0.001, respectively) at HYPOX10 compared to SL, and returned to baseline at 6MOM. TT level was strictly negatively correlated with BMI (p=0.02; r=-0.81), waist circumference (p=0.05; r=-0.75) and %fat (p=0.04; r=-0.78) at HYPOX10. A reduction of ejaculate volume and sperm concentration (p=0.05), with unchanged sperm forward motility, morphology, and DNA fragmentation (cytometric evaluation of TUNEL-positive sperm) were finally observed at HYPOX10, and normalised at 6MON. Conclusions Hypoxia induces negative effects on male fertility occurring through the reduction of important seminological parameters and indicating the influence of oxygen supply in physiological mechanisms of spermatogenesis. Furthermore, this study shows that prolonged altitude exercise is related to an adaptation of the endocrine system. Prolonged hypoxia during high-altitude trekking was associated to increased levels of TT, probably related to changes in body composition. This effect was shadowed, just after hypobaric trekking, by a possible negative testicular effect of hypoxia and physical endurance.