title: Chronome assessment of circulating melatonin in humans.
abstract: BACKGROUND
  Melatonin (MEL) production occurs mainly during the dark span. A prominent circadian variation is demonstrated in both blood and urine in humans.
  
  
  METHODS
  The circadian, circannual, age and gender patterns of MEL were concomitantly investigated in 40 men and 132 women, each providing blood samples every 4 hours for 24 hours for conventional and cosinor analysis.
  
  
  RESULTS
  Circulating MEL is circadian periodic (P < 0.001), peaking at night. The MESOR (rhythm-adjusted mean) is higher in women than in men. The circadian amplitude decreases with age. Both are modulated by a circannual variation, the MESOR peaking in winter (P < 0.001) and the circadian amplitude in summer (P < 0.05).
  
  
  CONCLUSIONS
  Samples, unqualified as to gender, age and/or season, incompletely characterize the circadian MEL patterns. This chronome approach detects changes that may escape detection otherwise, checking whether a value is too high or too low, and also whether "swinging" occurs to the right extent.
authors.affiliation: Cattedra di Medicina Interna, Universita degli Studi di Firenze, Florence, Italy.
authors.forename: B
authors.initials: B
authors.lastname: Tarquini
authors.forename: G
authors.initials: G
authors.lastname: Cornélissen
authors.forename: F
authors.initials: F
authors.lastname: Perfetto
authors.forename: R
authors.initials: R
authors.lastname: Tarquini
authors.forename: F
authors.initials: F
authors.lastname: Halberg
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000378:metabolism; D002940:Circadian Rhythm; D003920:Diabetes Mellitus / Q000097:blood; D005260:Female; D018149:Glucose Intolerance / Q000150:complications; D006801:Humans; D008297:Male; D008550:Melatonin / Q000097:blood*; D008875:Middle Aged; D010507:Periodicity; D012621:Seasons; D012727:Sex Characteristics
chemical_list: D008550:Melatonin