Plasma transferrin receptor levels and indices of erythropoiesis and iron status in healthy term infants.

PURPOSE

The goal of this study was to determine if the postnatal changes in plasma transferrin receptor (TfR) levels in healthy infants were associated with changes in erythropoiesis or iron status.

SUBJECTS AND METHODS

Longitudinal blood samples were obtained monthly from healthy term infants fed iron-fortified formula for the first 7 months and analyzed for plasma TfR and indices of erythropoiesis and iron status.

RESULTS

Plasma TfR level rose during the first 2 months of life (p < 0.002). When examined for its association with indices of erythropoiesis, plasma TfR was negatively associated with hemoglobin (Hb) (p < 0.01), and positively associated with plasma erythropoietin (EPO) concentration (p < 0.005) and absolute reticulocyte count (p < 0.005). Plasma TfR was not associated with erythrocyte protoporphyrin. Although indices of iron status were not suggestive of iron deficiency, plasma TfR was negatively associated with plasma ferritin, Tf saturation, and plasma iron, and positively associated with total iron binding capacity (TIBC) (p < 0.0001 for all).

CONCLUSIONS

Increases in plasma TfR levels were observed during normal infancy. The increases in plasma TfR levels correlate with increases in erythropoiesis without evidence for functional iron deficiency.