Melatonin, Circadian Rhythms, and Sleep

Disturbances in circadian rhythms often result in disturbances in sleep. Examples include syndromes in which sleep time is delayed or advanced, the sleeping problems associated with jet lag and shift work, and the sleep disorders that occur in totally blind persons with free-running circadian rhythms (i.e., rhythms that are not synchronized to the 24-hour day).1 The hormone melatonin can be used both to characterize and to treat such disorders.The circadian rhythm of melatonin secretion is generated by the central pacemaker, or “clock,” in the suprachiasmatic nuclei of the hypothalamus, and like many other circadian rhythms, it is synchronized to . . .