Effects of high-altitude hypoxia on the hormonal response to hypothalamic factors
Open Access
- 1 December 2010
- journal article
- Published by American Physiological Society in American Journal of Physiology-Regulatory, Integrative and Comparative Physiology
- Vol. 299 (6), R1685-R1692
- https://doi.org/10.1152/ajpregu.00484.2010
Abstract
Acute and chronic exposure to high altitude induces various physiological changes, including activation or inhibition of various hormonal systems. In response to activation processes, a desensitization of several pathways has been described, especially in the adrenergic system. In the present study, we aimed to assess whether the hypophyseal hormones are also subjected to a hypoxia-induced decrease in their response to hypothalamic factors. Basal levels of hormones and the responses of TSH, thyroid hormones, prolactin, sex hormones, and growth hormone to the injection of TRH, gonadotropin-releasing hormone, and growth hormone-releasing hormone (GHRH) were studied in eight men in normoxia and on prolonged exposure (3–4 days) to an altitude of 4,350 m. Thyroid hormones were elevated at altitude (+16 to +21%), while TSH levels were unchanged, and follicle-stimulating hormone and prolactin decreased, while leutinizing hormone was unchanged. Norepinephrine and cortisol levels were elevated, while no change was observed in levels of epinephrine, dopamine, growth hormone (GH), IGF-1, and IGFBP-3. The mean response to hypothalamic factors was similar in both altitudes for all studied hormones, although total T4 was lower in hypoxia during 45 to 60 min after injection. The effect of hypoxia on the hypophyseal response to hypothalamic factors was similar among subjects, except for the GH response to GHRH administration. We conclude that prolonged exposure to high-altitude hypoxia induces contrasted changes in hormonal levels, but the hypophyseal response to hypothalamic factors does not appear to be blunted.Keywords
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