PLASMA TRANSFERRIN RECEPTOR LEVELS AND INDEXES OF ERYTHROPOIESIS AND IRON STATUS IN HEALTHY TERM INFANTS

Purpose: The goal of this study was to determine if the postnatal chan ges in plasma transferrin receptor (TfR) levels in healthy infants wer e associated with changes in erythropoiesis or iron status. Subjects a nd Methods: Longitudinal blood samples were obtained monthly from heal thy term infants fed iron-fortified formula for the first 7 months and analyzed for plasma TW 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 erythropoie sis, plasma TW was negatively associated with hemoglobin (Hb) (p < 0.0 1), and positively associated with plasma erythropoietin (EPO) concent ration (p < 0.005) and absolute reticulocyte count (p < 0.005). plasma TfR was not associated with erythrocyte protoporphyrin. Although indi ces of iron status were not suggestive of iron deficiency, plasma TfR was negatively associated with plasma ferritin, Tf saturation, and pla sma iron, and positively associated with total iron binding capacity ( TIBC) (p < 0.0001 for all). Conclusions: Increases in plasma TfR level s were observed during normal infancy. The increases in plasma TfR lev els correlate with increases in erythropoiesis without evidence for fu nctional iron deficiency.