Amazingly, a group of investigators enrolled 25 healthy climbers to determine how hypoxia affects the expression of iron transporters in the duodenal mucosa (Hepatology 2013; 58: 2135-62).

Methods: In a nonblinded, prospective study, blood and duodenal samples were taken at three timepoints: baseline (446 meters) and at 4559 meters two days later after a rapid ascent and then at day four while remaining at high altitude. 14 subjects received dexamethasone on day 2 to avoid high-altitude sickness. The duodenal biopsies were obtained by unseated transnasal small-caliber duodenoscopy.  Numerous other assays were checked as well.

Key finding: Hypoxemia was associated with a 10-fold increase in duodenal expression of divalent metal-ion transporter 1 and ferroportin 1 which promote iron intake.  In addition, there was decreased serum hepcidin levels.

Take-home message: Hypoxic conditions such as high-altitude quickly lead to an activation of changes that lead to compensatory erythropoeisis.

Related blog post: Help with hepcidin | gutsandgrowth