Melatonin

Melatonin, or 5-methoxy-N-acetyltryptamine, is a hormone produced by pinealocytes in the pineal gland, located in the brain, but also in the retina and GI tract. It is a derivative of the amino acid tryptophan.

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Melatonin produced in the pineal gland acts as an endocrine hormone since it is released into the blood. On the other hand, melatonin produced by the retina and the GI tract is considered a paracrine hormone.

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Melatonin helps regulate sleep-wake or circadian rhythms. Normally, production of melatonin by the pineal gland is stimulated by darkness and inhibited by light. Melatonin can suppress libido by inhibiting secretion of luteinizing hormone (LH) and follicle stimulating hormone (FSH) from the anterior pituitary gland -- especially in mammals that have a breeding season when daylight hours are long, such as sheep. Nobel Prize laureate Julius Axelrod performed many of the seminal experiments elucidating the role of melatonin and the pineal gland in circadian rhythms. Beta blockers decrease nocturnal melatonin release.

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Melatonin is synthesized by various plants such as rice and ingested melatonin was shown to be capable of reaching and binding to melatonin binding sites in the brain of mammals http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7773197&dopt=Abstract.

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In recent times, melatonin has become available as a drug and a dietary supplement. It appears to have some use against insomnia, jet lag, and circadian misalignment. Melatonin is a powerful antioxidant which can easily cross cell membranes including the blood-brain barrier. It has been studied for the treatment of cancer, immune disorders, cardiovascular diseases, depression, seasonal affective disorder, and sexual dysfunction; the results of most of these studies remain inconclusive. However, it has been shown to clearly ameliorate seasonal affective disorder and circadian misalignment, in studies by Alfred J. Lewy (OHSU) and other researchers.

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Melatonin is referred to by some biochemists and human physiologists as the master hormone, because it regulates the production of most human hormones, both paracrine and endocrine. In addition, melatonin, taken alone, is an immunoregulator that enhances T cell production somewhat. However, when melatonin is taken in conjunction with calcium, it is a very potent immunostimulator of the T cell response. This is the reason it is used extensively as an adjuvant in many treatment protocols. Because it does not have to be prescribed, and since it is in the public domain, few doctors care to publicize its advantages. For the same reason, few clinical trials have been done to see its effectiveness in treating various diseases, such as cancer, obesity, h.i.v. infection, and others.

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To synthesize melatonin, serotonin is converted to N-acetylserotonin by the enzyme 5-HT N-acetyltransferase. N-acetylserotonin is then converted to melatonin by the enzyme 5-hydroxyindole-O-methyltransferase. See serotonin for details on how tryptophan is converted to serotonin.

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Melatonin has been shown to increase the lifespan of mice by 20% in some studies

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http://www.ceri.com/melaton.htm http://www.cris.com/~nubrain/melatonin.html http://www.lef.org/magazine/mag95/95dec3.htm http://www.demogr.mpg.de/general/structure/division1/lab-asm/118.htm.

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Other studies have noted that wearing garments such as bras are linked to a decrease in melatonin production. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11128295&dopt=Citation

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Acetyl: Acetyl is the radical of acetic acid, with chemical formula -COCH3. A molecule containing an acetyl group has the chemical structure...

Hormone: A hormone (from Greek horman - "to set in motion") is a chemical messenger from one cell (or group of cells) to another. All multicellular organisms produce hormones (including plants - see article phytohormone)....

Pinealocyte: Pinealocytes are the main cells of the pineal gland. They produce and secrete melatonin. Pinealocytes have an organelle called...