title: Higher concentrations of serum transferrin receptor in children than in adults.
abstract: BACKGROUND
  The serum transferrin receptor (TfR) concentration in adults is suggested to provide a sensitive measure of iron depletion and together with the serum ferritin concentration to indicate the entire range of iron status, 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 concentrations and their ratios in children and adults and look for correlations between TfR concentrations and other measures of iron status.
  
  
  METHODS
  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; 95% reference 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). Geometric mean TfR-ferritin ratios were higher in infants (316; 95% reference interval: 94, 1059) than in prepubertal boys (219; 78, 614) and higher in prepubertal boys than in men (72; 23, 223). By multiple linear regression analysis, the best predictors of TfR concentration were serum iron (P = 0.004) and log serum ferritin (P < 0.0001), both being inverse correlations (R2 = 0.32). Mean corpuscular volume, blood hemoglobin, transferrin iron saturation, transferrin, and even age seemed to not have an influence on the TfR concentration and erythropoiesis was not a determinant of TfR concentration.
  
  
  CONCLUSIONS
  Low serum ferritin and iron concentrations, even within the normal physiologic range, result in high TfR concentrations. The lower the iron stores, the stronger the influence of ferritin on TfR. A high TfR concentration in children, especially in infants, is a response to physiologically low iron stores. Age-specific reference concentrations for TfR are needed.
authors.affiliation: Department of Clinical Chemistry and Hospital for Children and Adolescents, University of Helsinki, Finland. marita.virtanen@huch.fi
authors.forename: M A
authors.initials: MA
authors.lastname: Virtanen
authors.forename: L U
authors.initials: LU
authors.lastname: Viinikka
authors.forename: M K
authors.initials: MK
authors.lastname: Virtanen
authors.forename: J C
authors.initials: JC
authors.lastname: Svahn
authors.forename: R M
authors.initials: RM
authors.lastname: Anttila
authors.forename: T
authors.initials: T
authors.lastname: Krusius
authors.forename: J D
authors.initials: JD
authors.lastname: Cook
authors.forename: I E
authors.initials: IE
authors.lastname: Axelsson
authors.forename: N C
authors.initials: NC
authors.lastname: Räihä
authors.forename: M A
authors.initials: MA
authors.lastname: Siimes
mesh_terms: D000328:Adult; D000367:Age Factors; D002648:Child; D004909:Erythrocyte Indices; D004920:Erythropoiesis; D005260:Female; D005293:Ferritins / Q000097:blood; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D007223:Infant; D007501:Iron / Q000097:blood; D008297:Male; D011990:Receptors, Transferrin / Q000097:blood*; D012044:Regression Analysis