Sleep Disorders and Melatonin

Abstract

Melatonin is an endogenously produced neurohormone that plays a key role in the signaling of daily rhythms and the coordination of these rhythms with the external world. It serves as a marker of darkness and also modulates circadian phase, or timing, through feedback mechanisms on the intrinsic circadian rhythm generated by the suprachiasmatic nucleus. Melatonin and its metabolites can be readily measured in plasma, saliva, and urine. Measurement of melatonin profi les, particularly, the timing of the sharp rise in melatonin levels during the biological night, can be used to assess circadian phase which is useful in the diagnosis of sleep/ circadian pathology as well as determining the optimal timing of treatment. Therapeutically, melatonin can be used to manipulate circadian phase and promote sleep in a circadian rhythm-dependent fashion. Randomized trials have demonstrated that exogenous melatonin can be of benefi t in a number of sleep disease states including delayed sleep phase syndrome, non-24-hour sleep-wake syndrome, jet lag, and insomnia. Keywords