The kidney and aldosterone in acclimatization at altitude.

Five climbers were studied during an ascent of a 7500 m mountain in the Hindu Kush. Representiative samples from 24-hour urines were preserved from five subjects at 5400 m and 6600 m and from two at 7000 m. Sodium and cortisol excretion was normal, but that of potassium and especially aldosterone was low, especially in two climbers who had episodes of peripheral oedema. Hypoaldosteronism is a feature of high altitude acclimatization but its cause and significance have still to be elucidated.