title: Serum reference values for leptin in healthy infants.
abstract: OBJECTIVE
  Reports on leptin concentrations in pediatric populations lack reference values for infants in the first months of life. Our study was conducted on healthy full-term infants between 2002 and 2012 to determine serum leptin reference values in subjects less than 18 months old.
  
  
  METHODS
  Routine outpatient blood tests for serum leptin were performed on 317 infants using a radioimmunoassay method. The median and 10th-90th percentiles were calculated to obtain reference values using quantile regression. Values established in this study were compared with another independent cohort of 110 infants.
  
  
  RESULTS
  The median (IQR) serum leptin concentration in the infants was 2.37 (3.26) ng/ml (n = 317). The median leptin concentration was 2.81 (3.49) ng/ml (n = 202) in infants younger than 6 months of age, 1.44 (2.27) ng/ml (n = 59) in infants between 6-12 months of age and 1.77 (2.05) ng/ml (n = 56) in infants between 12-18 months of age. We obtained leptin reference values based on age by estimating the lower and upper percentiles. In the entire cohort, the median (IQR) leptin concentration was 2.22 (3.11) ng/ml in males (n = 168) and 2.60 (3.32) ng/ml in females (n = 149). According to the type of feeding median serum leptin concentration was higher in breast-fed infants (n = 188) than in formula-fed infants (n = 129) (2.63 (3.34) ng/ml vs. 2.12 (2.77) ng/ml; p<0.05).
  
  
  CONCLUSIONS
  Our data revealed no gender difference in leptin concentration in early infancy. After 6 months of life, leptin concentrations decreased slightly. We used a large cohort to confirm that breast-fed infants had significantly higher serum leptin levels than formula-fed infants during the first 6 months of life, although this difference disappeared later in life. In this study, we defined the leptin reference range in healthy infants in the first 18 months of life according to the Clinical and Laboratory Standards Institute (CLSI).
authors.affiliation: Department of Paediatrics, University of Turin, Regina Margherita Children's Hospital, Turin, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Savino
authors.affiliation: Department of Paediatrics, University of Turin, Regina Margherita Children's Hospital, Turin, Italy.
authors.forename: Lorenza
authors.initials: L
authors.lastname: Rossi
authors.affiliation: Department of Paediatrics, University of Turin, Regina Margherita Children's Hospital, Turin, Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Benetti
authors.affiliation: Department of Paediatrics, University of Turin, Regina Margherita Children's Hospital, Turin, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Petrucci
authors.affiliation: Department of Paediatrics, University of Turin, Regina Margherita Children's Hospital, Turin, Italy.
authors.forename: Miriam
authors.initials: M
authors.lastname: Sorrenti
authors.affiliation: Department of Paediatrics, University of Turin, Regina Margherita Children's Hospital, Turin, Italy.
authors.forename: Leandra
authors.initials: L
authors.lastname: Silvestro
mesh_terms: D000367:Age Factors; D001903:Bottle Feeding; D001942:Breast Feeding; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007223:Infant; D041943:Infant Formula; D007231:Infant, Newborn; D020738:Leptin / Q000097:blood*; D008297:Male; D011863:Radioimmunoassay / Q000379:methods*; D012016:Reference Values
chemical_list: D020738:Leptin