| Several candidates have been suggested as the zeitgebers for peripheral clocks, including glucocorticoids, retinoic acid and melatonin. |
| Cherries are also a great source of melatonin, a hormone that your body uses to regulate its sleep patterns. |
| The onset of puberty appears to be triggered by changes in the blood melatonin level. |
| The pineal gland hormone, melatonin, is one of the endproducts regulated by the circadian system. |
| A second theory postulates that when melatonin levels are depressed, female hormones are increased. |
| Delaying sleep on weekends delays the nightly secretion of melatonin, the sleep hormone. |
