Melatonin: pharmacology, functions and therapeutic benefits.

Melatonin synchronizes central but also peripheral oscillators (fetal adrenal gland, pancreas, liver, kidney, heart, lung, fat, gut, etc.), allowing temporal organization of biological functions through circadian rhythms in relation to periodic environmental changes and therefore adaptation of the individual to his/her internal and external environment. Measures of melatonin are considered the best peripheral indices of human circadian timing. First, the pharmacology of melatonin (biosynthesis and circadian rhythms, pharmacokinetics and mechanisms of action) is described, allowing a better understanding of the short and long term effects of melatonin following its immediate or prolonged release. Then, various physiological effects of melatonin are reviewed, including detoxification of free radicals and antioxidant actions, bone formation and protection, reproduction, and cardiovascular, immune or body mass regulation. Given these physiological effects, potential benefits of melatonin use are discussed, especially with regard to brain or gastrointestinal protection, psychiatric disorders, cardiovascular diseases and oncostatic effects. This review highlights the high number and diversity of major melatonin effects and opens important perspectives for measuring melatonin as a biomarker (biomarker of early identification of certain disorders and also biomarker of their follow-up) and using melatonin with clinical preventive and therapeutic applications.