[Pituitary hormone responses to exercise at high altitudes]

Adrenal, thyroid and gonadal axes are affected at high altitude

Humans cannot live at very high altitude for reasons, which are not completely understood. Since these reasons are not restricted to cardiorespiratory changes alone, changes in the endocrine system might also be involved. Therefore, hormonal changes during prolonged hypobaric hypoxia were comprehensively assessed to determine effects of altitude and hypoxia on stress, thyroid and gonadal hypothalamus-pituitary hormone axes. Twenty-one male and 19 female participants were examined repetitively during a high-altitude expedition. Cortisol, prolactin, thyroid-stimulating hormone (TSH), fT4 and fT3 and in males follicle-stimulating hormone (FSH), luteinizing hormone (LH) and total testosterone were analysed as well as parameters of hypoxemia, such as SaO2 and paO2 at 550 m (baseline) (n = 40), during ascent at 4844 m (n = 38), 6022 m (n = 31) and 7050 m (n = 13), at 4844 m (n = 29) after acclimatization and after the expedition (n = 38). Correlation analysis of hormone concentrations with oxygen parameters and with altitude revealed statistical association in most cases only with altitude. Adrenal, thyroid and gonadal axes were affected by increasing altitude. Adrenal axis and prolactin were first supressed at 4844 m and then activated with increasing altitude; thyroid and gonadal axes were directly activated or suppressed respectively with increasing altitude. Acclimatisation at 4844 m led to normalization of adrenal and gonadal but not of thyroid axes. In conclusion, acclimatization partly leads to a normalization of the adrenal, thyroid and gonadal axes at around 5000 m. However, at higher altitude, endocrine dysregulation is pronounced and might contribute to the physical degradation found at high altitude.

Recent advances in hormonal response to exercise

1. This is an article concerning the maintenance of homeostasis during varying metabolic responses to different forms of physical stress. This can be considered the task of the nervous and endocrine systems. 2. Research during the past decade in the field of hormonal response to exercise (as a form of stress) in both exercise-trained and untrained subjects (mostly in the human and rat) is discussed. 3. The responses of the various hormones are discussed in three categories according to the broad chemical classification of the hormones, viz. the polypeptides, the amines and the steroids, although of course, these responses are highly integrated. 4. From the literature it is evident that exercise-trained individuals maintain homeostasis more efficiently than untrained individuals because of an improved integrated endocrine response to changes in homeostatic balance. 5. There seems to be insufficient research being conducted into the steroid hormones--especially in view of the increasing misuse of anabolic steroids in enhancing sports performance these days.