[The circadian system in man: From the internal clock to melatonin secretion]

Ann Pharm Fr. 2016 Sep;74(5):331-4. doi: 10.1016/j.pharma.2016.02.001. Epub 2016 Mar 15.
[Article in French]


The internal or biological clock which is located in the suprachiasmatic nuclei of the anterior hypothalamus is controlled by clock genes and environmental factors which are able to synchronize the clock to 24h. Rhythm desynchronization (shiftwork and nightwork, transmeridian flights, aging, some psychiatric diseases, blindness, intake of some drugs…) occurs when the internal clock does no longer work in harmony with the astronomical time i.e. our watch. The circadian system consists of three major elements, which are the clock, the retinohypothalamic tract and melatonin which is secreted by the pineal gland and considered as the arrow of the clock. Both light and melatonin present a phase response curve useful for the treatment of sleep circadian disorders.

Keywords: Clock; Désynchronisation; Horloge interne; Light; Lumière; Melatonin; Mélatonine; Rhythm desynchronization; Synchronisation; Synchronization.

Publication types

  • Review

MeSH terms

  • Biological Clocks / physiology*
  • Circadian Rhythm / physiology*
  • Humans
  • Melatonin / metabolism*
  • Melatonin / physiology*
  • Pineal Gland / physiology
  • Suprachiasmatic Nucleus / physiology


  • Melatonin