title: Maturation of the circadian rhythm of the adrenocortical functions in human neonates and infants.
abstract: The cortisol levels in the peripheral blood were measured radioimmunologically at 08.00, 12.00,. 16.00, 20.00, 24.00 and 04.00 h in human neonates and infants with ages of 1, 2 and 3 days, 1, 2 and 4 weeks, 2, 3 and 6 months and 1 and 3 years. During the first 2 days of extrauterine life the neonates had high plasma cortisol levels without a circadian rhythm. During the first 2 months there were decreased cortisol levels in the infants, but the diurnal rhythms were still absent, and free-running fluctuations were observed. The typical circadian rhythms of the plasma cortisol levels were present in infants aged 3 months; these rhythms were identical with the diurnal changes of 1- and 3-year-old infants. In the groups of patients studied the data suggest that the circadian rhythm of the adrenocortical function may develop to the adult-type pattern already during early infancy.
mesh_terms: D000302:Adrenal Cortex / Q000254:growth & development* / Q000378:metabolism; D000375:Aging; D002675:Child, Preschool; D002940:Circadian Rhythm; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D007223:Infant; D007231:Infant, Newborn
chemical_list: D006854:Hydrocortisone