Endocrine Abstracts

Objective: Acclimatization to high-altitude is a dynamic process affecting the neuro-endocrine and physiological systems. Psychological well-being is also influenced by hypobaric-hypoxia. Psychic stress is known to influence the hypothalamo–pituitary–adrenal/thyroid axis. However, the involvement/contribution of ‘psychological-performance’ on hormone changes at high-altitude is not known. The objective of this study was to examine: i) the effect of ethnicity on cortisol, thyroid hormones and psychological performance during high-altitude exposure in lowlanders as compared to sea-level, and with high-altitude-natives (HAN) at high-altitude; ii) if there is any relation between psychological variables and hormones at high-altitude in the Indian population.

Methods: Male volunteers (20–50 years) belonging to Caucasoid/Indo-European (n=25), Mongoloid/Tibeto-Burman (n=31) and Australoid/Dravidian (n=28) ethnicities were studied at sea-level and after 3–4 weeks of stay at ~4500 m. High-altitude-natives (HAN, n=21) were studied at ~4500 m only. Plasma hormone (EIA/ELISA)/biochemical estimation, physiological and psychological evaluation was conducted on all subjects. Significance at P<0.05.

Results: In lowlanders, there was a significant change in loneliness, fear-of-death; thyroid hormones at high-altitude. Interactive effect between high-altitude×ethnicity was observed for psychological and hormone variables (except hopelessness, freeT₃). Significant variation in hormones and psychological variables was observed between lowlanders and HAN at high-altitude (except memory, loneliness, TSH). Significant correlation was observed between fear-of-death/loneliness for Caucasoids (r=0.55) and Mongoloids (r=0.49); loneliness/freeT₄ (r=−0.37) and fear-of-death/freeT₄ (r=−0.36) for Mongoloids.

Conclusions: Thyroid hormones and emotionality during high-altitude acclimatization are influenced by ethnicity, and social-isolation/fear-of-death influences freeT₄.