Salivary testosterone concentration of Aymara men native to 3600 m.

This paper explores the possibility that variation in the normal physiological range of testosterone concentration modulates men's adaptation to hypobaric high-altitude hypoxia through stimulating haemoglobin production and/or causing respiratory disturbances and exacerbated hypoxaemia during sleep. These effects of testosterone are observed clinically at sea level and have potentially opposing consequences at high altitude, the former perhaps enhancing and the latter diminishing the effectiveness of adaptations to hypoxia. Seventeen young (average age 27 years) and 22 older (average age 57 years) healthy adult high altitude native Aymara men tested at 3600 m have average morning salivary testosterone concentrations of 282 and 241 pmol/l, respectively. The 31 urban men of both age groups have higher testosterone concentrations than the eight rural men and have mean haemoglobin concentrations significantly 0.7-1.0 g/dl higher within the normal high-altitude range, consistent with known effects of testosterone at sea level. Older urban men have slightly more frequent respiratory disturbances during sleep, associated with significantly greater hypoxaemia. There appear to be modest benefits to testosterone concentrations in the upper end of the observed range; however, the direction of these responses towards more haemoglobin production and more hypoxaemia during sleep of older men suggests the hypothesis that very high testosterone concentrations such as those in the upper ranges of sea level values could compromise adaptation to high altitude, particularly among older men.