Changes in arterial oxygen saturation (arterial SpO2, measured by pulse oximetry), hematologic markers of iron homeostasis, serum EPO, plasma sTfR, and GDF15 after a rapid ascent to high altitude. Baseline (0 hours) measurements were made in Lima, Peru (133 m above sea level), after which volunteers received an intravenous infusion of either 200 mg of iron sucrose (closed symbols, n = 12) or saline (open symbols, n = 12) and then ascended rapidly to high altitude (4340 m). *Significant difference between the change from baseline in the iron group, compared with the saline group (unpaired Student t test, P < .01). †,‡Significant change from baseline within the iron or saline group, respectively (paired Student t test, P < .05). Note that initial apparent “oversaturation” of transferrin (calculated transferrin saturation > 100%) can occur with intravenous administration of iron, reflecting the transient excess of serum iron. Symbols represent mean ± SEM.
