RELATIONS BETWEEN COMPONENTS OF ENDOCRINE SYSTEMS IN TIEN SHAN HIGHLAND INHABITANTS

Extreme environmental conditions are of special importance for the ecological studies of adaptation of humans to different natural and climatic conditions. Long term dwelling under extreme conditions is stressful and decreases the reserve of the endocrine system available for coping with adverse environmental conditions. The purpose of the present work was to study the conditions of the pituitary, thyroid, and sex glands and their relationships under stressful highland conditions. Blood levels of the pituitary hormones adre-nocorticotrophic factor and thyrotrophic factor, the adrenocortical hormone cortisol, the thyroid hormones thyroxin and triiodothy-ronin, the sex hormone testosterone, and the adrenal medullar catecholamine hormones were determined using immunoenzyme and fluorimetric techniques. In highlanders dwelling at 3600 meters above sea level, cortisol and ACTH are reduced evidencing a dec- reased activity of the pituitary-adrenal systems and, correspondingly, a more sparing way of body functioning. This is confirmed by decreased noradrenaline, dopamine and serotonin levels in people who live long under highland conditions. Increased TTH, T4 and noradrenaline in association with relatively low T3 may be a response to cold. Decreased testosterone in men and women suggests that the reserve capacities of the endocrine system have been mobilized and thus are restricted. The results show contrasting responses of endocrine glands to highland hypoxia. The mode and extent of the resulting rearrangements depend on the level of hypoxia and is determined by interrelationships between hormones. The endocrine system, as a base of forming the physiological and structural features of the body, ensures the specificity of protective response to highland stress by coherent integration of the functions of different regulatory systems, hormone playing the role of mediators between their central and peripheral components. The data expand and deepen the available knowledge about the endocrine mechanisms of adaptive responses of humans to different environmental factors and may be useful for defining the regional norms of human health relevant to highlands.

Tien-Shan, the natives of the highlands, hypoxia, coldness, the functional state, the pituitary-adrenal system, catecholamines, thyroid hormones, gonads