Circadian regulation of endocrine functions

The prominent circadian rhythms of the endocrine system are important for our broader understanding of physiology and behavior, in both health and disease. There is now much evidence that disruptions in the circadian domain, either due to external factors such as shift work or internal factors such as sleep disturbances, can lead to physiological and psychological pathologies. There is interest and urgency in understanding how time is coordinated in the body. A master circadian clock resides in the suprachiasmatic nucleus of the hypothalamus. While this is the only tissue in which autonomous rhythms are self-sustaining, the molecular machinery is present in most peripheral cells. Rather than imposing time on the body then, the SCN entrains local clocks in a tissue-specific manner. These peripheral clocks then participate in controlling rhythmic transcription of genes associated with local tissue function. In this review, we examine the interplay between brain and peripheral clocks in the control of endocrine rhythms.