Endocrine Abstracts

Background and objective: Adaptive process to hypoxia of altitude involves changes in the homeostatic steady state of several endocrine variables which precede and contribute- to many physiologic adaptations. Physiologic responses to altitude-stress exhibit ethnic variation. However, there has been limited characterization of ‘ethnicity effect’ on endocrine responses to high-altitude stress. This is true for enzyme-immunoassay method (EIA) of plasma hormone analysis. Little is known in this regard about the Indian population. Ethnic variation in physiologic and psychological performance during altitude-stress has been reported in this population. The objective of this study was to examine the effect of ethnicity on plasma stress hormones during high-altitude exposure in lowlanders as compared to sea-level, and with high-altitude natives (HAN) at high-altitude in the Indian population.

Methods: Healthy male soldiers (n=115) between 20–50 years were enrolled for the study. Lowlanders belonging to Rajput (n=25), Gorkha (n=30) and South-Indian (n=35) ethnicities were studied at sea-level and after 3–4 weeks of stay at ~4500 m. Ladakhis (HAN, n=25) were studied at ~4500 m only. Estimation of plasma cortisol-CORT, testosterone-T, prolactin-PRL, arginine vasopressin-AVP and proatrial natriuretic peptide-proANP_1–98 was measured by EIA.

Results: In lowlanders, there was a significant (P<.001) change in PRL, AVP and proANP_1–98 (within physiological-range) during high-altitude exposure. Also, ethnicity of the subject was found to have a significant (P<.001) effect on hormonal changes at high-altitude. Among lowlanders, difference in plasma hormones was observed between north- (Rajput, Gorkha) and South- Indians at high-altitude.

Except cortisol, significant (P<.001) variation in plasma hormones was observed between lowlanders and HAN at high-altitude.

Conclusions: Plasma stress hormone changes during high-altitude stress are influenced by ethnicity with regard to the Indian population.