Rearrangement of Neuroendocrine Systems in the Mountains

Abstract

The aim of this research was to study the functional state of the anterior pituitary, thyroid, adrenal, and reproductive glands and their relationship with chronic exposure to high altitude. Studies were conducted in high altitudes inhabitants of the Tien-Shan (1200 m, 2800 m, 3600 m). Adrenocorticotropic hormone (ACTH), cortisol, catecholamines, thyroid, and sex hormones were determined by immunosorbent and spectrofluorometric methods. Normal hormone levels for sea level inhabitants were used for comparison. Increased cortisol levels in mountaineers (M) (2800 m) may reflect a reduction in reserve capacity of the pituitary-adrenocortical system and the formation of their chronic condition or incomplete adaptation, or the continuing adaptation to the environment in a number of successive generations. Reduced activity of the pituitary-adrenocortical system in high altitude residents (HAR) at 3600 m is a consequence of the harsh weather conditions, narrowing the boundaries of the organism’s adaptation and facilitating economical and appropriate regulation. High altitude residents at 2800 m and 3600 m (when compared to the normal hormone levels and data of low mountain residents at 1200 m), presented a predominance of the mediator activity of the hormone sympathetic-adrenal system, showing an increased secretion of norepinephrine and dopamine, and a decreased secretion of epinephrine. Increased levels of norepinephrine are associated with its decreased metabolism and reserves, providing constant catecholamines that create the preconditions for a stable and long-term work of the body, providing an adequate state of physiological function. Features power (prevalence of carbohydrates and fats in food M and HAR) also lead to the activation secretion of norepinephrine, which leads to intensive use of the biological mediator precursor, dopamine, as evidenced by its high level in residents at both altitudes. This change in optimum reserve of catecholamines promotes an accelerated restoration of catecholamine levels. Prolonged exposure to high altitude hypoxia induces contrasting changes in thyroid hormone levels. The mountaineers (2800 m) are found close to the low values of normal TSH levels, whereas thyroid hormones tend to increase. The increase in T3 and T4 levels, while maintaining the basic concentration of TSH or small hyperthyroidism, seem necessary to adapt to the extreme conditions of high mountains. Increased levels of T4, TSH and norepinephrine, with a decreased secretion of T3 in HAR (3600 m), reflect an additional reaction on the PTS factor constant exposure to cold in the mountains. Low values ​​of T3 without changes in TSH and T4 levels are explained by the influence of cold. The detected levels of testosterone in male HAR (3600 m) show the adverse effects of environmental factors, and reduced levels of progesterone (89%) indicate a hard endocrine function of women M (2800 m), on the mobilization of the strategic reserve endocrine system. However, the decreased functional activity of the sex glands does not exceed the boundaries of conventional indicators, which are a reflection of the body’s resistance. Conclusion: Features of endocrine systems in high-population of Tien-Shan include reduced activity of the pituitary-adrenocortical system in the organism, and economical operation, which allows for normal life, work and heavy physical activities in the specific conditions of the mountains. The parameters of endocrine status should be assessed only in relation to its their own mountain normal population values.