Melatonin excretion, body temperature and subjective arousal during 64 hours of sleep deprivation

(1) Evidence has been presented, based on measurement of melatonin by radioimmunoassay in 12 healthy males, that the urinary excretion of melatonin follows a circadian pattern in humans during sleep deprivation when the subjects are exposed to light. (2) Melatonin excretion increased with increased sleep deprivation. (3) Melatonin excretion during recovery sleep did not differ from that during base line sleep. (4) Melatonin excretion did not react to psychosocial stress at trough times (as adrenaline did). (5) Self-rated fatigue and body temperature exhibited a circadian variation. (6) Peak fatigue and trough body temperature coincided temporally with the peak of melatonin excretion.