Higher concentrations of serum transferrin receptor in children than in adults

Background: The serum transferrin receptor (TfR) concentration in adults is suggested to provide a sensitive measure of iron depletion and together wi th the serum ferritin concentration to indicate the entire range of iron st atus, from iron deficiency to iron overload. However, little is known about TfR concentrations in children. Objective: Our objective was to compare serum TfR and ferritin concentratio ns and their ratios in children and adults and look for correlations betwee n TfR concentrations and other measures of iron status. Design: Our study groups were healthy 1-y-old infants (n = 36), 11-12-y-old prepubertal boys (n = 35), and 20-39-y-old men (n = 40). Results: TfR concentrations were higher in infants ((x) over bar; 95% refer ence interval: 7.8 mg/L; 4.5, 11.1) than in prepubertal boys (7.0 mg/L; 4.7 , 9.2) and higher in prepubertal boys than in men (5.8 mg/L; 3.1, 8.5). Geo metric mean TfR-ferritin ratios were higher in infants (316; 95% reference interval: 94, 1059) than in prepubertal boys (219; 78, 614) and higher in p repubertal boys than in men (72; 23, 223). By multiple linear regression an alysis, the best predictors of TfR concentration were serum iron (P = 0.004 ) and log serum ferritin (P < 0.0001), both being inverse correlations (R-2 = 0.32). Mean corpuscular volume, blood hemoglobin, transferrin iron satur ation, transferrin, and even age seemed to not have an influence on the TfR concentration and erythropoiesis was not a determinant of TfR concentratio n. Conclusions: Low serum ferritin and iron concentrations, even within the no rmal physiologic range, result in high TfR concentrations. The lower the ir on stores, the stronger the influence of ferritin on TfR. A high TfR concen tration in children, especially in infants, is a response to physiologicall y low iron stores. Age-specific reference concentrations for TfR are needed .