title: Effects of acutely displaced sleep on testosterone.
abstract: BACKGROUND
  It is not yet clear whether the diurnal variation in testosterone is regulated by circadian or homeostatic (sleep) influences.
  
  
  OBJECTIVE
  The present study tested whether testosterone is driven by a circadian-independent sleep effect by shifting sleep acutely to daytime in a 24-h sampling regiment.
  
  
  METHODS
  In the sleep laboratory, seven healthy young men (age, 22-32 yr) participated in three conditions: habituation (sleep between 2300-0700 h), night sleep (2300-0700 h), and day sleep (0700-1500 h), the latter two in a balanced order.
  
  
  METHODS
  Serum testosterone was, in all conditions, sampled by hourly blood drawing for 24 h during constant bed rest.
  
  
  RESULTS
  Mean testosterone levels increased as a log-linear function of time (hours) across both sleep periods (b = 4.88; P < 0.001), from 15.3 +/- 2.1 to 25.3 +/- 2.2 nmol/liter during night sleep and from 17.3 +/- 2.1 to 26.4 +/- 2.9 nmol/liter during day sleep. Similarly, mean testosterone levels decreased with time (log-linear) awake (b = -1.80; P < 0.001). There was also evidence of a weak circadian component (acrophase ranging between 0651-0924 h) and an increase with time in the laboratory. Moreover, all these effects, except for the increase during sleep, differed significantly between individuals.
  
  
  CONCLUSIONS
  In conclusion, testosterone increased during sleep and fell during waking, whereas circadian effects seemed marginal. Individual differences were pronounced.
authors.affiliation: National Institute for Psychosocial Medicine, 171 77 Stockholm, Sweden. john.axelsson@ipm.ki.se
authors.forename: John
authors.initials: J
authors.lastname: Axelsson
authors.forename: Michael
authors.initials: M
authors.lastname: Ingre
authors.forename: Torbjörn
authors.initials: T
authors.lastname: Akerstedt
authors.forename: Ulf
authors.initials: U
authors.lastname: Holmbäck
mesh_terms: D000328:Adult; D002940:Circadian Rhythm / Q000502:physiology*; D006801:Humans; D008297:Male; D012044:Regression Analysis; D012890:Sleep / Q000502:physiology*; D013739:Testosterone / Q000097:blood*; D014851:Wakefulness / Q000502:physiology*
chemical_list: D013739:Testosterone