title: Diurnal rhythm in serum leptin.
abstract: OBJECTIVE
  To assess 24-hour serum leptin levels in children.
  
  
  METHODS
  Five girls and two boys aged 10.4-13.6 (mean 12.2) years with pubertal stages I to III were studied. All children were healthy. A fasting blood sample was drawn at 08.00 hours, and thereafter samples were obtained every 2 hours throughout 24 hours until 08.00 hours the next morning. Serum leptin was measured by a specific radioimmunoassay.
  
  
  RESULTS
  A statistically significant circadian variation was found in mean leptin profile expressed as a percentage of overall day mean (F-ratio =10.4; P<0.001) with trough and peak levels (+/- SEM) at 10.00 (6.55+/-1.52 mg/l) and 24.00 hours (10.99+/-2.34 mg/l), respectively.
  
  
  CONCLUSIONS
  In normal children serum leptin levels exhibit a nocturnal increase and a decrease during the morning. The nocturnal rise may represent a time lagged stimulating effect of insulin. The diurnal rhythm needs to be considered when serum leptin is assessed in clinical studies.
authors.affiliation: Department of Paediatrics, Randers Hospital, Denmark.
authors.forename: O D
authors.initials: OD
authors.lastname: Wolthers
authors.forename: C
authors.initials: C
authors.lastname: Heuck
authors.forename: C
authors.initials: C
authors.lastname: Skjaerbaek
mesh_terms: D000293:Adolescent; D002648:Child; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D020738:Leptin / Q000097:blood*; D008297:Male; D011863:Radioimmunoassay; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D020738:Leptin