title: Emergence and evolution of the circadian rhythm of melatonin in children.
abstract: OBJECTIVE
  To assess the age at which the circadian rhythm of melatonin begins.
  
  
  METHODS
  55 children, divided into groups from the neonatal period to 24 months of life, were studied. Urine samples were taken from 28 newborn babies to measure 6-sulfatoxymelatonin (aMT6s). Salivary samples were collected from infants (27 cases), to measure melatonin (aMT). aMT was measured by RIA and aMT6s by ELISA using commercial kits. Changes in the levels of aMT6s and aMT were evaluated using the Friedman test and Wilcoxon matched pair test.
  
  
  RESULTS
  The group aged 27-41 days showed statistically significant differences in daily aMT6s and aMT concentrations. The highest values were always found between 24.00 and 8.00 h. This day/night difference persisted from 2-3 to 13-24 months of age.
  
  
  CONCLUSIONS
  The data indicate that the circadian melatonin rhythm appears at the end of the neonatal period and persists thereafter.
authors.affiliation: Department of Pediatrics, University Hospital, University of Valladolid, Spain. ardura@ped.uva.es
authors.forename: Julio
authors.initials: J
authors.lastname: Ardura
authors.forename: Regina
authors.initials: R
authors.lastname: Gutierrez
authors.forename: Jesus
authors.initials: J
authors.lastname: Andres
authors.forename: Teresa
authors.initials: T
authors.lastname: Agapito
mesh_terms: D000375:Aging / Q000378:metabolism; D005075:Biological Evolution; D002940:Circadian Rhythm / Q000502:physiology*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008027:Light; D008297:Male; D008550:Melatonin / Q000378:metabolism* / Q000652:urine; D009043:Motor Activity / Q000502:physiology; D017440:Photoperiod; D011446:Prospective Studies; D011863:Radioimmunoassay; D012463:Saliva / Q000378:metabolism; D012890:Sleep / Q000502:physiology
chemical_list: D008550:Melatonin