Neurodegenerative diseases melatonin

Melatonin secretion is synchronized to the light/dark (LD) cycle, with a nocturnal maximum (in young humans, about 200 pg/ml plasma) and low diurnal baseline levels (about 10 pg/ml plasma). Studies have supported the value of the exogenous administration of melatonin in circadian rhythm sleep disorders, insomnia, cancer, neurodegenerative diseases, disorders of the immune function, and oxidative damage (Karasek et al. 2002 Pandi-Perumal et al. 2005, 2006 Srinivasan et al. 2005a,b, 2006 Hardeland et al. 2006). 

Because melatonin is sold over the counter and its production is not the subject of strict regulation as is that of prescribed medications, it is in wide use, but insufficient scientifically controlled information is available. Another consequence of the popularity and availability of the hormone is its use in a wide array of situations in which its efficacy has not been proven yet for instance, as treatment for neurodegenerative diseases or as a sleep-inducing medication. It also has been tried as an antidepressant, but that effect is still unclear. The administration of melatonin to patients with bipolar depression, especially to rapid cyclers, is of interest, especially if its use is associated with the presumed decrease in nocturnal hormonal levels and increase in sensitivity to light (Lewy et al. 1985). The possibility that melatonin also serves as a stabilizer of rhythm in these patients is in accord with the homeostatic effect of several other hormones that have been previously discussed here. 

Srinivasan V, Pandi-Perumal SR, Maestroni GJM, Esquifino AI, Hardeland R, Cardinal DP (2005) Role of melatonin in neurodegenerative diseases. Neurotox Res 74 293-318... 

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