Where is MELATONIN produced?

Pineal Gland

MELATONIN is produced and secreted by the pineal gland under control of the hypothalamus mainly when it is dark.     Light/dark status is provided by the hypothalamic “Master Clock”

The Biological Clock

-   A pea-sized, pinecone-shaped organ located in the exact center of the brain - this gland is the first to form during human fetal development, being clearly distinguishable a mere three weeks after conception.

-   Composed of pinealocytes (pineal cells).   With a rich supply of adrenergic nerve fibers that influence its secretions.

-    MELATONIN is the only hormone secreted by the pineal gland.   Secreted by pineal parenchymal cells into the general circulation and into the cerebrospinal fluid, when stimulated by NOREPINEPHRINE. MELATONIN is an indoleamine compound, derived from the amino acid tryptophan, with SEROTONIN being its immediate precursor. MELATONIN was discovered when it was found to lighten amphibian skin.

-    MELATONIN secretion is regulated by Sympathetic nervous System (SNS), increased in response to darkness.   Tightly controlled by the hypothalamic circadian pacemaker (“Master biological clock”), MELATONIN thus provides a hormonal signal of night-time darkness; MELATONIN secretion is also increased in response to hypoglycemia.

-   MELATONIN is not stored in the pineal gland.   We cannot rely on yesterday's MELATONIN for today; it leaves the gland through simple diffusion with a short half-life during the initial few minutes, followed by a second longer phase. We need a liberal supply of MELATONIN each evening

Retina, Lens, GI tract, skin +

MELATONIN can also be produced directly by the retina, lens, GI tract, skin and other tissues/cells (E.g. bone marrow cells, lymphocytes and epithelial cells are not regulated by light/dark).    These cells do not DIRECTLY release MELATONIN into the blood, but act on local target cells (i.e. by paracrine action).

-    MELATONIN produced by enterochromaffin cells of the GI mucosa represents the most important extra-pineal source of MELATONIN.   The GI tract secretes ~400 times the amount of the pineal gland.

•   MELATONIN affects GI motility, is protective of duodenal epithelium and pancreas, prevents GERD and ulcers, and much more

•   MELATONIN produced by enterochromaffin cells contributes quite significantly to circulatory levels of MELATONIN -however,“. . .basal daytime melatonin levels and the extent of their elevation at nighttime appear to be additionally controlled by nutritional factors, such as the amount and the composition of ingested food and therefore availability of tryptophan as a rate-limiting precursor of melatonin formation by the enterochromaffin cells of the gastrointestinal tract.”

G. Huether. The contribution of extrapineal sites of melatonin synthesis to circulating melatonin levels in higher vertebrates. Experientia 15. 8. 1993, Volume 49, Issue 8, pp 665-670 Springerlink

•  Although, MELATONIN acts directly on the GI organs  it is the MELATONIN that enters circulation from the GI tract, which seems to have the predominant, although indirect effect on GI organs, via the brain-gut axis.

MELATONIN Health Benefits