“Live high‐train low” induced changes in hemoglobin mass and the erythropoietin‐erythroferrone‐hepcidin axis in female endurance athletes

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The effects of a 21‐day live high‐train low (LHTL) on hemoglobin mass (Hb mass ) and iron demand including the erythropoietin (EPO)‐erythroferrone (ERFE)‐hepcidin axis and routine iron markers were investigated. Fifteen female endurance athletes completed either 21‐day LHTL in normobaric hypoxia (2500 m, ~18 h·day −1 ) (INT, n = 8) or lived and trained in normoxia (CON, n = 7). Hb mass and resting blood were collected before and after the intervention. An additional blood sample was collected on Day 6 for INT. 21‐day LHTL increased Hb mass 3.8% in INT ( p < 0.001). EPO increased 35.6% from Day 0 to Day 6 in INT ( p = 0.037) and then decreased 42.4% from Day 6 to Day 21 ( p = 0.019). In INT, no changes were detected in ERFE or hepcidin, and from the routine iron markers only serum transferrin receptor increased from Day 0 to Day 21 (13.9%, p = 0.013). In CON, no changes were detected in Hb mass or iron markers. In INT, Hb mass and ferritin were positively associated (Day 0 to Day 6, p = 0.005). Thus, hepcidin and ERFE may not provide additional information regarding iron demand following 6‐ or 21‐day LHTL compared to routine iron markers. The relationship between Hb mass and ferritin indicates that adequate ferritin levels are needed during hypoxia to support hematological adaptations.