Melatonin

Melatonin is a neurohormone produced by the pineal gland, and its primary function is believed to be regulating sleep. This hormone is produced from the moment we close our eyes.

In the presence of light, however, a neuro-endocrine message is sent, blocking its formation. Therefore, the secretion of this substance is almost exclusively determined by photosensitive structures, primarily at night.

Melatonin is classified as an indolamine and has serotonin, an important neurotransmitter, as its precursor. It is speculated that the photoreceptive structures of the retina and the pineal gland produce Melatonin by modifying the serotonin synthesis pathway through an enzyme, serotonin-N-acetyltransferase. Circulating Melatonin would act on the various systems of the body, preparing and inducing sleep. This Melatonin production apparatus is present in vertebrates in general.

It is also believed that maternal Melatonin can help control the infant's sleep cycle. Research has shown that babies exhibit synchrony with their mothers. As Melatonin is present in breast milk, and its concentration is higher at night, babies sleep more with milk offered at night.

For restorative sleep, it is essential that Melatonin is adequately secreted by the pineal gland. It is also presumed that Melatonin performs other functions, such as regulating body temperature and influencing sexual behavior.

As with serotonin, Melatonin is also produced from an amino acid called Tryptophan, normally ingested in a balanced diet. Thus, the sequence would be Tryptophan transforming into Serotonin, and this into Melatonin. This explains why the concentration of Serotonin increases in the pineal gland during the day, while there is light, inversely to what occurs with Melatonin.

As we have seen, Melatonin production is directly linked to the presence of light. When light strikes the retina, the optic nerve and other neuronal connections transmit this information to the pineal gland, inhibiting Melatonin production. The highest production of Melatonin occurs at night, between 2:00 and 3:00 AM, in a normal rhythm of life, and this increased production induces sleep.

During normal sleep, where much of the body's energy and organic balance is restored, in addition to adequate Melatonin production, other concomitant phenomena occur, among which we can mention:

Melatonin reaches its peak production at 3 years of age and significantly declines between 60 and 70 years, which leads to poor sleep quality in the elderly. At 60, we have half the amount of Melatonin we had at 20, and around 70, levels are very low in many people, almost zero.

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