Physiology and pharmacology of melatonin in relation to biological rhythms

Pharmacol Rep. 2009 May-Jun;61(3):383-410. doi: 10.1016/s1734-1140(09)70081-7.


Melatonin is an evolutionarily conserved molecule that serves a time-keeping function in various species. In vertebrates, melatonin is produced predominantly by the pineal gland with a marked circadian rhythm that is governed by the central circadian pacemaker (biological clock) in the suprachiasmatic nuclei of the hypothalamus. High levels of melatonin are normally found at night, and low levels are seen during daylight hours. As a consequence, melatonin has been called the "darkness hormone". This review surveys the current state of knowledge regarding the regulation of melatonin synthesis, receptor expression, and function. In particular, it addresses the physiological, pathological, and therapeutic aspects of melatonin in humans, with an emphasis on biological rhythms.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Animals
  • Arylalkylamine N-Acetyltransferase / physiology
  • Circadian Rhythm / drug effects*
  • Circadian Rhythm / physiology*
  • Depression / drug therapy
  • Depression / physiopathology
  • Humans
  • Light Signal Transduction
  • Melatonin / biosynthesis
  • Melatonin / pharmacology*
  • Melatonin / physiology*
  • Melatonin / therapeutic use
  • Molecular Structure
  • Photoperiod
  • Pineal Gland / physiology*
  • Pineal Gland / physiopathology
  • Receptors, Melatonin / agonists
  • Receptors, Melatonin / antagonists & inhibitors
  • Receptors, Melatonin / classification
  • Receptors, Melatonin / metabolism
  • Seasons
  • Sleep Wake Disorders / drug therapy
  • Sleep Wake Disorders / physiopathology
  • Suprachiasmatic Nucleus / metabolism
  • Suprachiasmatic Nucleus / physiology


  • Receptors, Melatonin
  • Arylalkylamine N-Acetyltransferase
  • Melatonin