Melatonin – metabolism and the role of pineal hormone

Abstract

Melatonin is a hormone mostly produced in the pineal gland. Its essential role is to regulate human circadian rhythm. Endogenous tryptophan is converted into melatonin. The transformation consists of 4 stages during which the serotonin is produced. The concentration of melatonin depends on age and lighting conditions – blue light suppresses a production of the hormone. In children and the elderly melatonin level never reaches maximum concentration while in adults it is reached between midnight and 3 am. Melatonin is mainly catabolised in a liver and eliminated with urine and faeces. It is also oxidized by free radicals. Bioavailability is about 15% if taken orally. With age, the production of endogenous melatonin decreases, mainly due to the progressive calcification of the pineal gland. Similar disorder is observed in the shift workers. The circadian rhythms disruptions can lead to diabetes mellitus, obesity, and neoplastic diseases. One of the reasons of that is disturbed synthesis and secretion of melatonin, which is a subject of scientific studies.