Using a recently developed model for investigating the neuroendocrine role of
melatonin in man, we studied
melatonin's effect on the nocturnal secretion of
thyrotropin and
cortisol in 17 normal male volunteers. The model consists of sleep in the dark and all-night
sleep deprivation in conditions of: bright light with and without a
melatonin infusion, and dim light. We have improved our infusion paradigm so that levels of
melatonin during infusion are now indistinguishable from those occurring during sleep in the dark or dim light
sleep deprivation.
Sleep deprivation per se raised TSH levels compared to normal sleep. However, the three conditions of
sleep deprivation could not be distinguished from each other, which suggests that the suppression of TSH by sleep (or the stimulation of TSH by
sleep deprivation) is not mediated by
melatonin.
Cortisol secretion was unaffected by
sleep deprivation regardless of
melatonin's presence or absence. However, a difference in the pattern of secretion of
cortisol in the sleep condition in the early morning (compared to the
sleep deprivation conditions) was noted. These data do not implicate
melatonin in the acute regulation of TSH or
cortisol in normal man. These data also provide a method of
melatonin infusion that replicates the pattern and levels seen in sleep.