PINEAL GLAND: FUNCTIONS, ANATOMY, DISEASES - NEUROPSYCHOLOGY - 2025

The pineal gland, cerebral epiphysis, coranium or pineal body, is a small gland that is located inside the brain of almost all species of vertebrates. In humans, its size is comparable to that of a grain of rice (about 8 millimeters long and about 5 wide). In adults, its weight is around 150 mg.

Its name comes from its shape, which resembles that of a pineapple (the fruits that come from the pine tree). It is located in the center of the brain, between both cerebral hemispheres in an area called the epithalamus, on the roof of the third cerebral ventricle.

Pineal gland (red)

In humans, the pineal gland forms around the seventh week of gestation. It grows until the second year of life, although its weight increases until adolescence. Its blood flow is very abundant and comes from the choroidal branches of the posterior cerebral artery.

Although it is a gland, its histology is very similar to the structure of nervous tissue, consisting mainly of astrocytes and pinealocytes surrounded by a layer of pia mater. However, this structure is not protected by the blood-brain barrier, which means that drugs can access it more easily.

Pineal gland (green). Source: own work user: Anatomist90 CC BY-SA (http://creativecommons.org/licenses/by-sa/3.0/)

Astrocytes are a class of neuroglia that protect and support neurons, in this case, pinealocytes. The latter are a class of secretory cells that release melatonin and are only found in the pineal gland. On the other hand, the pia mater is the innermost layer of the meninges, and its function is to protect the brain and spinal cord.

Despite the curiosity that it has aroused throughout history, its true functions were discovered very late. In fact, the tasks of the pineal gland are the latest to be discovered of all the endocrine organs.

The functions of the pineal gland are primarily endocrine, regulating the sleep-wake cycles through the production of melatonin. It also participates in regulating our adaptation to seasonal rhythms, stress, physical performance, and mood. Also, it influences sex hormones.

History of the pineal gland

The pineal gland has been known for centuries, although much remains to be known about its exact function.

Traditionally, it has long been conceived as a "link between the spiritual world and the physical world." It has been associated with a higher level of consciousness and a link to the metaphysical universe.

The first description found of the pineal gland was made by Herophilus of Alexandria in the third century BC, who thought that it served to regulate the "flow of thought." In the 2nd century BC, Galen described its anatomy, calling it konarium (meaning pineapple cone) a term that still remains. (Guerrero, Carrillo-Vico and Lardone, 2007).

The philosopher René Descartes, considered it as the "seat of the soul and the place where our thoughts are formed." Some speak of it in a mystical way calling it "the third eye" because of its connection to light.

In the seventeenth century this idea of ​​Descartes about the pineal gland had little scientific support. During the eighteenth century, little by little interest in this structure was lost, coming to be considered a vestige that had no use.

However, at the beginning of the 20th century and thanks to the advancement of comparative anatomy, the first scientific data on the endocrine functions of the pineal gland began to be published. Specifically, a relationship between tumors in this structure and precocious puberty began to be observed.

In 1958 Aaron B. Lerner and his colleagues managed to isolate melatonin, the hormone produced by this gland. Thus, it was concluded that the pineal gland was a “neuroendocrine transducer”, which means that it transforms the light information of the retina into a neuroendocrine response (release of melatonin).

Melatonin acts as a neurotransmitter in our brain, regulating our biological clock.

Functions of the pineal gland

Today it is known that the pineal gland has a very high biochemical activity since it not only releases melatonin, but also serotonin, norepinephrine, histamine, vasopressin, oxytocin, somatostatin, luteinizing homone, follicle stimulant, prolactin, etc.

Therefore, the pineal gland can be considered as a neuroendocrine structure that synthesizes and secretes substances that exert a hormonal function in different organs and tissues of the body. Among them are the hypothalamus, pituitary, thyroid, gonads, etc.

Regulation of circadian rhythms

A vast, complex and still full of unknowns system is involved in the activation of the pineal gland. What is known is that its operation appears to be altered by light and dark. Apparently, so that we can see, the photoreceptor cells in the retina of the eyes release nerve signals to the brain.

These cells are connected with the suprachiasmatic nucleus of the hypothalamus, stimulating it. This stimulation inhibits the paraventricular nucleus of the hypothalamus when it is daytime, making us active.

However, at night and in the absence of light, the paraventricular nucleus “unlocks” and begins to send nerve signals to sympathetic neurons in the spinal cord. From there, signals are sent to the upper cervical ganglion, generating norepinephrine, a neurotransmitter that stimulates the pinealocytes of the pineal gland.

What happens when pinealocytes are stimulated? There is an increase in the production and release of melatonin. When this hormone enters the bloodstream and travels through the body, it causes the need to sleep.

In this way, the pineal gland secretes melatonin in order to help control the circadian rhythm. It has been found to have an ability to resynchronize the circadian rhythm in situations such as jet lag, blindness, or shift work.

The secretion of melatonin during the night varies throughout life, appearing after 2 months of life. Levels rise rapidly until they are 3-5 years old, and then decline until puberty. In adulthood they stabilize, and decline again in old age until it practically disappears.

Regulation of sex hormones

Melatonin appears to be related to sexual maturation in humans. In addition, it acts as a seasonal endocrine marker for the reproduction of seasonal species.

In rodents it has been observed that if the pineal gland is removed, puberty appears very early. While an exposure to short days delays sexual maturation. Thus, the administration of melatonin can induce advances or delays in the development of the gonads depending on the species, time or form of administration.

In humans, it appears that precocious puberty is associated with tumors that damage pineal cells, decreasing melatonin secretion. While an excessive secretion of this substance has been linked to pubertal delays.

Thus, it has been observed that an increase in melatonin produced by the pineal gland blocks the secretion of gonadotropins. These are those hormones that are involved in the development and function of the ovaries and testes (such as luteinizing hormone and follicle-stimulating hormone).

Participation in the effects of drugs and drugs

It has been shown in rodent studies that the pineal gland can modulate the effects of drugs of abuse. For example, it influences the mechanism of sensitization to cocaine.

In addition, it appears to act on the actions of the antidepressant fluoxetine (Prozac). In particular, in some patients this drug produces symptoms of anxiety at first.

Dimethyltryptamine (DMT), a potent psychedelic found naturally in living plants, is also believed to be synthesized in the pineal gland. However, this is not known with certainty and it is being given a mystical meaning that raises many doubts.

Immunostimulating action

Although it is not entirely proven, the hormone melatonin secreted by the pineal gland could participate by modulating the different cells involved in the immune system.

It has been shown to carry out multiple tasks associated with the morphology and functionality of both the primary and secondary organs of this system.

In this way, it would strengthen our body's ability to combat potentially harmful external agents.

Antineoplastic effect

Melatonin is related to the ability to inhibit tumor growth, that is, it is considered oncostatic.

This has been observed in experiments with in vivo and in vitro tumor models. Above all, in those related to hormones; such as breast, endometrial and prostate cancer. On the other hand, it also enhances other antitumor therapies.

These effects are also not known with absolute certainty and more research is lacking to prove it.

Antioxidant action

A link has also been found between the pineal gland and the elimination of free radicals, exerting an antioxidant effect. This would decrease the macromolecular damage in the different organs. In addition, it seems to enhance the effect of other antioxidants and enzymes with this same function.

Influences aging and longevity

The pineal gland (by regulating melatonin levels) can induce or delay aging and quality of life. This could be due to its antioxidant, cancer cell growth inhibitor and immunomodulatory properties.

In different investigations it was observed that the administration of melatonin to adult rats prolonged their life between 10 and 15%. Whereas, if a pinealectomy (removal of the pineal gland) was performed, it was shortened by a similar percentage.

In a study carried out in 1996, it was shown in rats that the pineal hormone melatonin is a neuroprotective, that is, it prevents the neurodegeneration typical of aging or diseases such as Alzheimer's.

For all these benefits, many people have chosen to start a melatonin treatment on their own. It should be noted that this can have unknown and even dangerous effects, since many of these properties are not sufficiently demonstrated.

As mentioned, most of the research is done on rodents and has not been done on humans.

Calcification of the pineal gland

Very high resolution micrograph of a normal pineal gland. Source: Kleinschmidt-DeMasters BK, Prayson RA (November 2006). "An algorithmic approach to the brain biopsy – part I". Arch. Pathol. Lab. Med. CC BY-SA (http://creativecommons.org/licenses/by-sa/3.0/)

Calcification is the main problem of the pineal gland, since it is an organ that tends to accumulate fluoride. As the years go by, phosphate crystals form and the gland hardens. This hardening leads to less melatonin production. For this reason, the sleep-wake cycles are altered in old age.

There is even research that indicates that the hardening of the pineal gland produced by fluoride advances sexual development, especially in girls (Luke, 1997).

Pineal gland with calcifications Source: onw work user: Difu Wu CC BY-SA (http://creativecommons.org/licenses/by-sa/3.0/)

It appears that the secretions of the pineal gland block the development of the reproductive glands. If this gland is not activated, there is an acceleration in the development of the sexual organs and the skeleton.

This could be somewhat alarming, since in a 1982 study it was found that 40% of American children who were under 17 years old were in a process of pineal calcification. This calcification has even already been observed in children as young as 2 years old.

Calcification of the pineal gland has also been linked to the development of Alzheimer's disease and certain kinds of migraines. In addition to fluoride, it has also been seen that chlorine, phosphorus and bromine, in addition to calcium, can accumulate in the pineal gland.

If you do not have enough vitamin D (the one that is produced with sunlight), calcium cannot be bioavailable in the body. On the contrary, it would begin to calcify in the different tissues of the body (including the pineal gland).

So that this does not occur, in addition to controlling our levels of vitamin D, in an article by Global Healing Center they advise eliminating fluoride. Thus, you should use fluoride-free toothpaste, drink filtered water, and take calcium-rich foods rather than calcium supplements.

Pineal gland tumors

Pineal tumor

Although it is very rare, tumors can appear in this gland, which are called pinealomas. In turn, they are classified into pineoblastomas, pineocytomas and mixed, according to their severity. Histologically they are similar to those arising in the testes (seminomas) and in the ovaries (dysgerminomas).

These tumors can cause conditions such as Parinaud's syndrome (deficit in ocular mobility), hydrocephalus; and symptoms such as headache, cognitive and visual disturbances. A tumor in this area is very difficult to remove surgically because of its position.

References

1. Alonso, R., Abreu, P., & Morera, A. (1999). The pineal gland. Human Physiology (3rd Ed.) McGRAW-HILL INTERAMERICANA, 880.
2. Everything You Wanted to Know About the Pineal Gland. (May 3, 2015). Obtained from Global Healing Center: globalhealingcenter.com.
3. Guerrero, JM, Carrillo-Vico, A., & Lardone, PJ (2007). Melatonin. Research and Science, 373, 30-38.
4. López-Muñoz, F., Marín, F., & Álamo, C. (2010). The historical development of the pineal gland: II. From the seat of the soul to the neuroendocrine organ. Rev Neurol, 50 (2), 117-125.
5. Luke, JA (1997). The effect of fluoride on the physiology of the pineal gland (Doctoral dissertation, University of Surrey).
6. Manev, H., Uz, T., Kharlamov, A., & Joo, JY (1996). Increased brain damage after stroke or excitotoxic seizures in melatonin-deficient rats. The FASEB journal, 10 (13), 1546-1551.
7. Pineal Gland. (sf). Retrieved on December 28, 2016, from Wikipedia.
8. Pineal Gland. (sf). Retrieved on December 28, 2016, from Innerbody: innerbody.com.
9. Sargis, R. (October 6, 2014). An Overview of the Pineal Gland. Obtained from EndocrineWeb: endocrineweb.com.
10. Uz, T., Akhisaroglu, M., Ahmed, R., & Manev, H. (2003). The Pineal Gland is Critical for Circadian Period I Expression in the Striatum and for Circadian Cocaine Sensitization in Mice. Neuropsychopharmacology.
11. Uz, T., Dimitrijevic, N., Akhisaroglu, M., Imbesi, M., Kurtuncu, M., & Manev, H. (2004). The pineal gland and anxiogenic-like action of fluoxetine in mice. Neuroreport, 15 (4), 691-694.
12. Zimmerman RA, Bilaniuk LT. (1982). Age-related incidence of pineal calcification detected by computed tomography. Radiology; 142 (3): 659-62.