What does the pineal gland do? In mammals its main job is to turn darkness into a chemical signal: each night it makes melatonin, and the length of that signal tells the body how long the night is. The gland cannot see light itself; its instructions come from the eyes by way of the spinal cord.
This guide covers anatomy, the light-to-melatonin pathway, receptors, seasons (including a study at Canada’s northernmost station), calcification, history, myths and the pineal peptide research.
The short answer
- Its main job is night-time melatonin production. The pineal gland is a small, unpaired gland in the epithalamus whose pinealocytes make melatonin in darkness and secrete it into the blood and cerebrospinal fluid.
- Light reaches it through the eyes. Melanopsin-containing retinal ganglion cells signal the suprachiasmatic nucleus; the message then runs via the hypothalamus, thoracic spinal cord and superior cervical ganglion.
- Noradrenaline is the trigger. At night it acts on beta-1 adrenergic receptors, cyclic AMP rises, and the enzymes AANAT and ASMT turn serotonin into melatonin.
- Light at night shuts production down. In rats, AANAT is broken down by the proteasome within minutes of light; in people, light suppresses melatonin secretion.
- Melatonin signals darkness and is not a peptide. It is a small indoleamine that acts on two G protein-coupled receptors, MT1 and MT2, and its nightly duration tracks the length of the night.
- Calcification is common. “Brain sand” is found in most adults in imaging surveys; reversing it remains speculation.
- The pineal peptide research is thin. Epithalamin, Epitalon and Pinealon rest mainly on cell and animal work from one St. Petersburg group.
Pineal gland
Pineal body · epiphysis cerebri · Descartes’s “conarion”
- What it is
- A small, unpaired endocrine gland of the epithalamus, attached to the back of the third ventricle
- Size
- About 5–9 mm long; under 0.2 g in adults
- Main cells
- Pinealocytes, with astrocytes and other glia
- Main product
- Melatonin, an indoleamine made from tryptophan; not a peptide
- Controlled by
- Light and dark, relayed from the retina through a sympathetic pathway
- Hormone receptors
- MT1 and MT2, both G protein-coupled
- Name
- Greek kônarion, from its likeness to a stone-pine nut, as Galen explained
Where the evidence stands
- Anatomy and pathway mapped
- Light control shown in people
- Seasonal signal shown in animals
- Peptide effects shown in people
The physiology is textbook; the peptide claims rest on cell and animal work.
What does the pineal gland do?
The pineal gland is a small endocrine gland near the centre of the brain. It belongs to the epithalamus and is attached to the back of the third ventricle, between the posterior and habenular commissures. In adults it is about 5 to 9 mm long, roughly the size of a soybean, and weighs less than 0.2 grams. Its tissue is mostly pinealocytes with supporting astrocytes, and its blood supply, from the posterior choroidal arteries, is unusually rich: a 2018 review compares its blood filtration rate to the kidney’s. As a circumventricular organ with fenestrated capillaries, it lies outside the tight blood–brain barrier that seals most brain tissue.
In mammals, the most firmly established answer to what the pineal gland does is a single job: it makes melatonin at night and secretes it directly into the blood and cerebrospinal fluid. Most of what is known about pineal gland function follows from that. Melatonin is not a peptide but a small indoleamine built from tryptophan by way of serotonin; our guide to peptides vs small molecules explains why that distinction matters in the lab.
How light controls melatonin production
The mammalian pineal gland does not detect light by itself; its information comes from the eyes.
Sensing. In 2002, Hattar and colleagues showed that a subset of retinal ganglion cells contain the photopigment melanopsin, are intrinsically photosensitive, and send axons through the retinohypothalamic tract to the suprachiasmatic nucleus (SCN), the master circadian clock. Rods and cones are not required for the clock to lock onto the light–dark cycle.
Relaying. The SCN signals the paraventricular nucleus (PVN) of the hypothalamus, whose fibres descend to the intermediolateral cell column of the thoracic spinal cord. From there, neurons project to the superior cervical ganglia in the neck, and sympathetic fibres climb back to the gland through the nervi conarii. The detour matters: a 2000 study found no detectable melatonin in three people with complete tetraplegia, whose cervical cord injury lies on this route, while their cortisol and thyrotropin rhythms were preserved.
Synthesizing. At night the nerve endings release noradrenaline onto beta-1 and alpha adrenergic receptors, and cyclic AMP rises. That drives arylalkylamine N-acetyltransferase (AANAT), which acetylates serotonin’s nitrogen to make N-acetylserotonin, the same kind of chemistry seen in N-acetyl peptides. This step is generally considered rate-limiting, and AANAT activity rises 10- to 100-fold at night across vertebrates. Hydroxyindole-O-methyltransferase (HIOMT, also called ASMT) then makes melatonin.
Stopping. In 1970, Klein and Weller found rat pineal N-acetyltransferase more than 15 times more active at night than by day, a rhythm suppressed by constant light. In 1998, Gastel and colleagues showed that light at night, or blocking beta-adrenergic receptors, makes AANAT activity and protein fall rapidly; in cultured glands a cyclic AMP analogue or proteasome inhibitors prevented the fall, so the enzyme is actively destroyed. In people, Lewy and colleagues reported in 1980 that light suppresses melatonin secretion.
| Step | Signal or enzyme | What light at night does |
|---|---|---|
| Retina | Melanopsin in intrinsically photosensitive ganglion cells | Activates them |
| SCN | Master clock, reached via the retinohypothalamic tract | Entrains the clock and inhibits the relay |
| PVN, spinal cord, ganglion | Sympathetic relay through the thoracic cord and the neck | Sympathetic drive to the gland falls |
| Pinealocyte | Noradrenaline at beta-1 and alpha receptors; cyclic AMP rises | Stimulation stops; in rats, blocking beta receptors mimics light |
| AANAT | Serotonin to N-acetylserotonin; generally considered rate-limiting | Protein destroyed by the proteasome within minutes (rats) |
| ASMT (HIOMT) | N-acetylserotonin to melatonin | Output falls with AANAT |
| Release | Directly into blood and cerebrospinal fluid | In people, secretion is suppressed |
Melatonin as the signal of darkness
Melatonin is often called a sleep hormone; a 2020 review describes it more broadly as “the chemical expression of darkness”. It is secreted at night even in rats, which are nocturnal, so the body reads from it the timing and length of the night.
MT1 and MT2 receptors
Melatonin acts mainly through two G protein-coupled receptors, MT1 and MT2, as classified by the International Union of Basic and Clinical Pharmacology. A melatonin receptor cloned in 1994 from the skin pigment cells of the African clawed frog proved to be a GPCR that inhibited cyclic AMP accumulation in cultured cells: a fitting echo of the 1958 paper that isolated melatonin as the pineal factor “that lightens melanocytes”.
Night length and the seasons
Because melatonin is secreted at night, its duration varies inversely with day length. Seasonal mammals use that duration to read the time of year, with the pars tuberalis of the pituitary and the SCN as candidate decoding sites. Thomas Wehr’s group showed that human melatonin secretion also lengthens or shortens with artificial nights, yet urban men at 39°N showed no summer–winter difference, which the authors attributed to modern artificial lighting.
A Canadian case: Alert, Nunavut
Canadian Forces Station Alert, on Ellesmere Island at 82°30′N, is described by the Government of Canada as the most northerly permanently inhabited location in the world; it has no direct sunlight from about October 10 to March 1 and no night from about April 8 to September 5. When DRDC Toronto measured salivary melatonin, sampled under dim light, in station personnel in January and June 2012 (14 and 12 people), neither total melatonin nor its duration differed significantly between seasons, though the authors noted non-significant trends in small groups. Indoor life and artificial light complicate any simple link between latitude and melatonin.
A caution for mouse work. Many commonly used laboratory mouse strains do not produce melatonin, so check the strain first.
Pinealon, Illumineuro and other neuro research peptides are stocked as laboratory reagents, priced in CAD.
Browse cognitive & neuroPineal gland calcification
Pineal concretions, called corpora arenacea, acervuli or “brain sand”, are calcified deposits made mainly of hydroxyapatite, with a calcium-to-phosphorus ratio like that of tooth enamel. Figures compiled in a 2018 review put visible calcification at about 2% of people under 10, 53% at 20–29 and 83% over 30; studies in Turkey, Iran and Ethiopia each found about 70%; and 62% of 346 unselected patients showed it on CT. The review argues that rates are underestimated, since susceptibility-weighted MRI and PET reveal very small concretions. It also reports that melatonin and its urinary metabolite are lower in people with larger calcifications, an association rather than proof of cause. Separately, Luke found in 11 aged cadavers that pineal tissue held far more fluoride than muscle, tracking its calcium content; that 2001 study measured composition, not function.
From Galen and Descartes to 1958
Galen explained that the gland owes its name, kônarion, to its likeness to a stone-pine nut, and rejected the idea that it controlled the flow of psychic pneuma. Descartes, in the Dioptrics (1637), letters of 1640–41 and The Passions of the Soul (1649), made it the “principal seat of the soul”, reasoning that it was the one part of the brain that is not double and was small, light and easily moved. Thomas Willis doubted this, and in 1669 Nicolaus Steno pointed out that Descartes had the anatomy wrong. The modern, chemical story begins in 1958, when Aaron Lerner and colleagues isolated melatonin.
Third eye, DMT and decalcifying: myths vs evidence
| Claim | What the evidence shows |
|---|---|
| “The pineal gland is a third eye.” | The mammalian pineal gland does not detect light itself; it relies on the retina and the relay above. A true third eye, the parietal eye, exists in the tuatara and many lizards: it sits in an opening on top of the skull, with a lens and a simplified retina. None of this supports spiritual “third eye” claims. |
| “The pineal gland floods the brain with DMT.” | A 2019 rat study found N,N-dimethyltryptamine (DMT) in visual-cortex fluid sampled by microdialysis at low nanomolar levels, below serotonin, rising after experimental cardiac arrest. Levels were similar in rats without a pineal gland, and no human levels were measured. A 2018 review concluded that claims of pineal DMT release at birth, in dreams or near death are unsupported. |
| “You can decalcify your pineal gland.” | Fluoride does accumulate in calcified pineal tissue, but that says nothing about reversal. The 2018 review that discusses “rejuvenation” of the gland presents decalcification only as speculation, and we found no controlled human study showing that any diet, supplement or practice reverses it. |
| “Peptides reactivate the pineal gland.” | The pineal peptide literature below is mostly cell and animal work from one group, not evidence of any effect on the human pineal gland. |
The pineal peptides: epithalamin, Epitalon and Pinealon
Most “pineal peptide” research traces to Vladimir Khavinson’s group at the St. Petersburg Institute of Bioregulation and Gerontology, where, by the group’s own account, peptide bioregulators were created and studied more than 40 years ago. Our guide to reading a peptide study explains the caveats.
Epithalamin and Epitalon
Epithalamin is a polypeptide preparation from the pineal gland; Epitalon (also spelled Epithalon) is the synthetic tetrapeptide Ala-Glu-Asp-Gly, AEDG in one-letter amino acid code, based on it. A 2003 report from the group said Epitalon induced telomerase activity and telomere elongation in human somatic cells (see telomeres and telomerase). In 2025, authors outside the group reported telomere lengthening with higher hTERT expression in normal human fibroblast and epithelial cell lines, and lengthening through alternative lengthening of telomeres (ALT) in breast cancer cell lines; a correction followed. The group’s 2020 paper states that AEDG “increased melatonin synthesis in the pineal gland during ageing”, citing earlier pinealocyte-culture and rat studies rather than testing it: the developers’ own summary, not an independent finding, and not evidence about the human pineal gland. Our Epitalon research guide has the detail.
Pinealon
Pinealon is the synthetic tripeptide Glu-Asp-Arg (EDR) from the same program. In a 2011 study it reduced reactive oxygen species build-up, in a concentration-dependent way, and necrotic cell death in cerebellar granule cells, neutrophils and PC12 cells under oxidative stress; the authors’ proposal that it acts directly on the genome remains a hypothesis. A 2012 rat study of diet-induced prenatal hyperhomocysteinemia reported better spatial learning and less reactive oxygen species build-up in the offspring of the Pinealon group. Despite its name, the Pinealon work we found concerns neurons and oxidative stress, not the pineal gland; see our Pinealon research guide.
What’s established and what isn’t
Reasonably well established
- The pineal gland makes melatonin at night and secretes it into the blood and cerebrospinal fluid.
- Light reaches it indirectly, through the retina-to-spinal-cord relay.
- Noradrenaline and cyclic AMP drive AANAT; in rats, light at night triggers its proteasomal breakdown.
- Light suppresses human melatonin secretion; in a small study, melatonin was undetectable in complete tetraplegia.
- Melatonin duration encodes photoperiod in seasonal mammals.
- Pineal calcification is common and more prevalent with age.
Open questions
- How closely human melatonin tracks the seasons under modern lighting, in Canada or elsewhere.
- Whether calcification lowers melatonin output or merely accompanies other changes.
- Whether brain DMT has a physiological role, and what, if anything, the pineal contributes.
- Whether decalcification is possible at all.
- Whether Epitalon’s cell-culture telomere effects occur in living tissue, and what the cancer-cell ALT result means.
- Independent replication of the pineal peptide animal work, and any controlled human data.
Sourcing pineal-related research peptides in Canada
If you are buying research peptides in Canada for work on these short peptides, the documentation questions are standard, plus a few specific to very short sequences.
- Confirm identity by mass. With three or four residues, a mass-spectrometry check against the expected mass is the clearest confirmation; see how LC-MS confirms identity.
- Check acetylated forms separately. A certificate for N-Acetyl Epithalon should report the acetylated mass.
- For blends, ask what the certificate covers. A co-formulated vial such as Illumineuro needs data for each component; see what a blend’s certificate can prove.
- Match the batch number on the certificate to your vial, as our peptide COA guide explains.
- Store cold, dry and dark, lyophilized until needed; see the peptide storage guide.
PinealonThe Glu-Asp-Arg tripeptide, studied mainly in neuronal oxidative-stress modelsView product
EpithalonAla-Glu-Asp-Gly, based on the pineal preparation epithalaminView product
N-Acetyl EpithalonThe same tetrapeptide with an acetyl group on its N-terminusView product
Illumineuro BlendPinealon blended with N-Acetyl Selank, N-Acetyl Semax and PE-22-28View product
Research use only. Pure Peptides Canada products are laboratory reagents for in-vitro research, not for human or veterinary use. This article explains published research for education; it is not medical, dietary or dosing guidance.
Frequently asked questions
What does the pineal gland do?
In mammals, the pineal gland’s most firmly established job is making melatonin at night. Its pinealocytes convert serotonin into melatonin in darkness and secrete it into the blood, and the duration of that signal tells the body how long the night is. Light at the eyes switches production off.
Where is the pineal gland located?
It sits near the centre of the brain as part of the epithalamus, attached to the back of the third ventricle. In adults it is about 5 to 9 mm long and weighs less than 0.2 grams. Its fenestrated capillaries place it outside the tight blood-brain barrier.
Is the pineal gland a third eye?
Not in mammals. The human pineal gland does not detect light itself; it learns about light and dark from the retina through a relay that runs down the spinal cord and back up through the neck. A true third eye, the parietal eye, exists in the tuatara and many lizards.
What is pineal gland calcification, and can it be reversed?
It is the build-up of hydroxyapatite deposits, known as brain sand, inside the gland. It becomes more common with age; figures compiled in a 2018 review reach about 83% in people over 30. Decalcification remains speculation, and we found no controlled human study showing that anything reverses it.
Does the pineal gland produce DMT?
The evidence does not support the popular claim. A 2019 rat study found low nanomolar DMT in visual-cortex fluid, but levels were similar in rats without a pineal gland, and no human levels were measured. A 2018 review concluded that the minute brain concentrations detected are not sufficient to produce psychoactive effects.
Is melatonin a peptide hormone?
No. Melatonin is a small indoleamine made from the amino acid tryptophan by way of serotonin, with the last two steps catalyzed by AANAT and ASMT. Peptide hormones, by contrast, are chains of amino acids joined by peptide bonds.
Cognitive and neuro research peptides, shipped from inside Canada
Pinealon, Illumineuro and the rest of the neuro range are priced in Canadian dollars and ship tracked from inside Canada by Canada Post Xpresspost in 3–7 days ($25 CAD), or free in 4–12 days on orders over $299. Pay by credit or debit card, Interac e-Transfer or cryptocurrency.
References
- Lerner AB, Case JD, Takahashi Y, Lee TH, Mori W. Isolation of melatonin, the pineal gland factor that lightens melanocytes. J Am Chem Soc. 1958;80(10):2587. DOI
- Klein DC, Weller JL. Indole metabolism in the pineal gland: a circadian rhythm in N-acetyltransferase. Science. 1970;169(3950):1093–1095. DOI
- Lewy AJ, Wehr TA, Goodwin FK, Newsome DA, Markey SP. Light suppresses melatonin secretion in humans. Science. 1980;210(4475):1267–1269. DOI
- Ebisawa T, Karne S, Lerner MR, Reppert SM. Expression cloning of a high-affinity melatonin receptor from Xenopus dermal melanophores. Proc Natl Acad Sci USA. 1994;91(13):6133–6137. DOI
- Wehr TA, Giesen HA, Moul DE, Turner EH, Schwartz PJ. Suppression of men’s responses to seasonal changes in day length by modern artificial lighting. Am J Physiol Regul Integr Comp Physiol. 1995;269(1):R173–R178. DOI
- Gastel JA, Roseboom PH, Rinaldi PA, Weller JL, Klein DC. Melatonin production: proteasomal proteolysis in serotonin N-acetyltransferase regulation. Science. 1998;279(5355):1358–1360. DOI
- Zeitzer JM, Ayas NT, Shea SA, Brown R, Czeisler CA. Absence of detectable melatonin and preservation of cortisol and thyrotropin rhythms in tetraplegia. J Clin Endocrinol Metab. 2000;85(6):2189–2196. DOI
- Goldman BD. Mammalian photoperiodic system: formal properties and neuroendocrine mechanisms of photoperiodic time measurement. J Biol Rhythms. 2001;16(4):283–301. DOI
- Luke J. Fluoride deposition in the aged human pineal gland. Caries Res. 2001;35(2):125–128. DOI
- Hattar S, Liao H-W, Takao M, Berson DM, Yau K-W. Melanopsin-containing retinal ganglion cells: architecture, projections, and intrinsic photosensitivity. Science. 2002;295(5557):1065–1070. DOI
- Khavinson VKh, Bondarev IE, Butyugov AA. Epithalon peptide induces telomerase activity and telomere elongation in human somatic cells. Bull Exp Biol Med. 2003;135(6):590–592. DOI
- Dubocovich ML, Delagrange P, Krause DN, et al. International Union of Basic and Clinical Pharmacology. LXXV. Nomenclature, classification, and pharmacology of G protein-coupled melatonin receptors. Pharmacol Rev. 2010;62(3):343–380. DOI
- Khavinson V, Ribakova Y, Kulebiakin K, et al. Pinealon increases cell viability by suppression of free radical levels and activating proliferative processes. Rejuvenation Res. 2011;14(5):535–541. DOI
- Arutjunyan A, Kozina L, Stvolinskiy S, Bulygina Y, Mashkina A, Khavinson V. Pinealon protects the rat offspring from prenatal hyperhomocysteinemia. Int J Clin Exp Med. 2012;5(2):179–185. PubMed Central
- Paul MA, Love RJ, Hawton AM, et al. Melatonin production, sleep patterns and modeled performance effectiveness in subjects in the high Arctic. Scientific Report DRDC-RDDC-2014-R15. Toronto: Defence Research and Development Canada; 2014. PDF
- Tan DX, Xu B, Zhou X, Reiter RJ. Pineal calcification, melatonin production, aging, associated health consequences and rejuvenation of the pineal gland. Molecules. 2018;23(2):301. DOI
- Nichols DE. N,N-dimethyltryptamine and the pineal gland: separating fact from myth. J Psychopharmacol. 2018;32(1):30–36. DOI
- Dean JG, Liu T, Huff S, et al. Biosynthesis and extracellular concentrations of N,N-dimethyltryptamine (DMT) in mammalian brain. Sci Rep. 2019;9:9333. DOI
- Gheban BA, Rosca IA, Crisan M. The morphological and functional characteristics of the pineal gland. Med Pharm Rep. 2019;92(3):226–234. DOI
- Lumsden SC, Clarkson AN, Cakmak YO. Neuromodulation of the pineal gland via electrical stimulation of its sympathetic innervation pathway. Front Neurosci. 2020;14:264. DOI
- Khavinson V, Diomede F, Mironova E, et al. AEDG peptide (Epitalon) stimulates gene expression and protein synthesis during neurogenesis: possible epigenetic mechanism. Molecules. 2020;25(3):609. DOI
- Al-dulaimi S, Thomas R, Matta S, Roberts T. Epitalon increases telomere length in human cell lines through telomerase upregulation or ALT activity. Biogerontology. 2025;26(5):178. DOI. Correction: DOI
- Romero RD, de Souza FSJ. Evolution of pineal nonvisual opsins in lizards and the tuatara and identification of lepidopsin: a new opsin gene. Genome Biol Evol. 2025;17(5):evaf058. DOI
- Lokhorst G-J. Descartes and the pineal gland. Stanford Encyclopedia of Philosophy, Summer 2026 archive edition (first published 2005; substantive revision 2013). Entry
- Government of Canada, Royal Canadian Air Force. Canadian Forces Station Alert. Canada.ca. Page
For laboratory research use only. Not for human or veterinary use. This article summarizes published research for educational purposes and is not medical advice.
