Changes in male reproductive function after high altitude mountaineering.

The male reproductive functions of the members of the Masherbrum (7821 m) Expedition in 1999 were examined via semen analyses and endocrine tests. Specimens were collected from three subjects who had stayed above 5100 m for 21 to 24 days and above 6700 m for 4 to 5 days before departure and 1 month, 3 months, and 2 yr after returning from the expedition. Semen analyses showed no change in the semen volume. Sperm counts decreased after 1 month and had not recovered after 3 months, but they had recovered after 2 yr in all subjects. An increase in abnormally shaped sperm was also observed after 1 month, but had nearly recovered to the preexpedition state after 3 months. Endocrine tests revealed slightly decreased testosterone in the blood after 1 month, which had decreased still further after 3 months. The tests were completely normal after 2 yr. We suggest that a high altitude sojourn may induce reversible spermatogenic and Leydig cell dysfunction.