Erythropoietin concentrations during 10 days of normobaric hypoxia under controlled environmental circumstances

Serum erythropoietin levels (s-[epo]), haemoglobin concentration ([Hb]), haematocrit (hct), and ferritin concentration ([fer]) were measured in seven healthy male volunteers (20-23 years) exposed continuously to hypoxia (PO2 14 kPa) for 10 days. Serum erythropoietin concentration increased significantly from 9.5+/-3.51 to 33.6+/-11.64 U L-1 (P<0.05) after 2 days of hypoxia. Thereafter, s-[epo] decreased. However, after 10 days s-[epo] was 18.7±5.83 U L-1 which was still increased above the pre-hypoxia level (P<0.05). Serum haemoglobin concentration and hct increased over the 10 days of hypoxia, [Hb] from 152+/-8.9 to 168+/-9.2 gL(-1) (P<0.001), and hct from 43±2.4 to 49±2.6% (P<0.001). Ferritin concentration decreased significantly during the hypoxic exposure from 82+/-46.9 to 44+/-31.7 mmol L-1 after 10 days (P<0.01). In conclusion, the initial increase of s-[epo] under controlled normobaric hypoxia was marked, 353%, and levelled off after 5-10 days at 62-97% above normoxia level. There was also a significant increase in [Hb] and hct and a decrease in [fer] after 10 days of exposure to normobaric hypoxia.