title: Lack of adult-type salivary cortisol circadian rhythm in hospitalized preterm infants.
abstract: OBJECTIVE
  Knowledge of the presence or absence of cortisol (F) circadian rhythm in preterm infants is important for the interpretation of F measurements made in samples taken for both clinical and research purposes. Little is known about its emergence in very preterm infants. This study examines circadian rhythm in F secretion in hospitalized infants born before 30 weeks' gestation.
  
  
  METHODS
  
  
  
  METHODS
  Prospective longitudinal observational study.
  
  
  METHODS
  11 infants admitted consecutively and born before 30 completed weeks of gestation.
  
  
  METHODS
  F was measured by highly specific radioimmunoassay on morning and evening saliva samples gathered at weekly intervals until discharged home. Circadian rhythm was defined as > or =40% reduction from morning to evening level.
  
  
  RESULTS
  For all data, the median salivary F was 10.3 nmol/l (range <0.5-372.8). F levels were highest in the first 3 weeks of life. No infants displayed classical circadian rhythm for 4 weeks or more prior to being discharged from hospital. The other infants showed randomly distributed morning and evening F values with a trend in 4 infants towards periods of consistently higher evening than morning values.
  
  
  CONCLUSIONS
  Adult-type F circadian rhythm is rarely evident in hospitalized preterm infants born before 30 weeks' gestation.
authors.affiliation: Department of Child Life and Health, University of Edinburgh and Neonatal Unit, Simpson Center for Reproductive Health, Royal Infirmary Edinburgh, Edinburgh, UK.
authors.forename: Susan
authors.initials: S
authors.lastname: Kidd
authors.forename: Paula
authors.initials: P
authors.lastname: Midgley
authors.forename: Mary
authors.initials: M
authors.lastname: Nicol
authors.forename: John
authors.initials: J
authors.lastname: Smith
authors.forename: Neil
authors.initials: N
authors.lastname: McIntosh
mesh_terms: D002940:Circadian Rhythm / Q000502:physiology*; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000097:blood / Q000378:metabolism*; D007030:Hypothalamo-Hypophyseal System / Q000502:physiology; D007231:Infant, Newborn; D007234:Infant, Premature / Q000097:blood / Q000378:metabolism / Q000502:physiology*; D008137:Longitudinal Studies; D008297:Male; D010913:Pituitary-Adrenal System / Q000502:physiology; D011446:Prospective Studies; D012463:Saliva / Q000737:chemistry; D018709:Statistics, Nonparametric
chemical_list: D006854:Hydrocortisone