Proceedings of The Physiological Society
University of Manchester (2010) Proc Physiol Soc 19, PC293
Hormone pattern in two ethnic groups of Tibetan ancestry
M. Sachidhanandam1, H. shree G1, S. Singh1, A. Salhan1, U. Ray1
1. Environmental Physiology, Defence Institute of Physiology and Allied Sciences, Delhi, Delhi, India.
Table 1. Hormone levels in ALL and HA natives at HA, and in sea level natives<\#13>
(*) represents significant variation between ALL and HA natives [General Linear Model -Multivariate analysis], (#) represents significant variation between ALL and sea level natives [unpaired t test], ($) represents significant variation between HA natives and sea level natives [unpaired t test].
Indigenous high-altitude (HA) populations (i.e. Andean, Tibetan and Ethiopian) exhibit different patterns of adaptation (e.g. haemoglobin concentration, oxygen saturation) to hypobaric hypoxia - the unique stress at HA. Long-term physiologic adaptations to altitude stress are mediated by hormonal alterations. Two ethnic groups of the Himalayas - Gorkha (submountainous people) and Ladakhi (HA natives) of the Indian population are considered to be of Tibetan origin. The aim of the study is to examine the pattern of hormonal adaptation to HA stress in Gorkha and Ladakhi ethnicities. Comparisons of hormone level in these groups with sea level natives belonging to different morpho-linguistic type (i.e. Australoid-Dravidian) were also studied. Subjects were male soldiers between 20 to 30 years of age. Investigations were carried out in: (i) Gorkhas (n=25) residing at ~4500m for ~6months (acclimatized lowlander, ALL), (ii) HA natives (n=25) at ~4500m, (iii) sea level natives (n=25) born and brought-up at sea level without any exposure to HA. Plasma levels of cortisol, testosterone, prolactin, thyroid stimulating hormone (TSH), triiodothyronine (T3), thyroxine (T4), free T3 and free T4 were measured by enzyme immunoassay/enzyme-linked immunosorbent assay. Table 1 summarizes the results of the study. Values are mean ± S.D. Level of statistical significance is p < .05. The findings demonstrate a difference in hormone adaptation to HA stress between Gorkhas and Ladakhis. This could be due to the fact that Ladakhis never had any exposure to sea level. On the other hand, Gorkhas of this study have been exposed to sea level. Thus, re-exposure to HA might have triggered defense mechanisms (e.g. increased adrenergic activity) to adapt to the new environment. This together with physical stress might have contributed to different endocrine pattern of adaptation in Gorkhas. Variation between Gorkhas and sea level natives is present for all hormones except TSH. Between Ladakhis and sea level natives, variations are observed for testosterone, T3, fT3 and T4. Thus, hormone adaptation to HA stress in Gorkhas and Ladakhis are different. Ladakhis differ from sea level pattern of hormone levels.
Where applicable, experiments conform with Society ethical requirements