High altitude exposure leads to a marked natriuresis and diuresis facilitated by a reduced resting and subdued post-exercise aldosterone. There is a strong correlation between aldosterone and cortisol at high altitude and although most, but not all, investigators report a rise in cortisol with ascent very little data exist regarding the post-exercise response in cortisol. We therefore measured salivary cortisol in a cohort of 45 subjects post-exercise and 20 subjects at rest with ascent to >5000 m in Nepal. Morning resting cortisol ( nmol/l, mean+/SD) rose between 4270 m and 5150 m (3.5±2.1 to 14.5±30.3 respectively, P=0.002). Post-exercise an initial drop in salivary cortisol between sea-level and 4270 m (P=0.01) and 3400 m and 4270 m (P=0.001) occurred followed by a significant rise in post-exercise cortisol between 4270 m and 5150 m (P<0.001). There were no significant associations between severity of Acute Mountain Sickness and cortisol levels. There was a significant correlation between cortisol post-exercise at 5150 m and oxygen saturation at 5150 m (rho=−0.451, P=0.004). In conclusion, this is the largest cohort to have their resting and post-exercise cortisol levels ascertained at high altitude. We confirm the previous findings of an elevated resting cortisol at >5000 m but present the novel finding that the post-exercise cortisol response to HA is suppressed at 4270 m in line with previous reports regarding aldosterone. The mechanism involved remains to be elucidated but may relate to a disconnection between ACTH and cortisol akin to that of renin and aldosterone at high altitude.
Declaration of interest: There is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.
Funding: No specific grant from any funding agency in the public, commercial or not-for-profit sector.