The pineal gland, which produces the body’s melatonin, is located deep within the brain. Melatonin is an influential hormone that helps to regulate sleep, wakefulness, and circadian patterns, which have broad effects on health.

This article discusses the pineal gland, including its location, the function of the pineal body, and conditions that can affect the pineal gland.

 

What Is the Pineal Gland?

The pineal gland is a neuroendocrine organ located in the brain that primarily produces melatonin, a hormone released in response to a lack of light. It is responsible for the body’s circadian rhythms.1

Like all parts of the endocrine system, the pineal gland makes hormones. The hormones produced by organs and glands of the endocrine system control vital functions like growth, development, reproduction, metabolism, and more.2 In addition to the pineal gland, organs and glands of the endocrine system include the following:

• Hypothalamus
• Pituitary gland
• Thyroid
• Thymus
• Adrenal gland
• Pancreas
• Ovaries
• Testes
• Placenta

 

Where Is the Pineal Gland Located?

The pineal gland (or pineal body) is a small organ that lies within the roof of the third ventricle, deep within the brain. Autopsy studies have shown that the average size of the pineal gland is similar to that of a grain of rice.

It is located within an area called the epithalamus, just behind the thalamus and above the cerebellum, resting at the back of the brain, near the brain stem. A small fluid-filled structure projects into the pineal gland, allowing the hormones it produces to more easily diffuse throughout the brain.

 

What Is the Structure of the Pineal Gland?

The pineal gland is often described as shaped like a pine cone. It is small, about 5-9mm long and 1-5mm wide, and reddish-grey.

The cells that make up the pineal gland tissue in humans and other mammals include hormone-producing pinealocytes and supportive interstitial cells.

 

What Is the Function of the Pineal Gland?

The pineal gland’s most crucial function is producing melatonin, a hormone that it makes in response to darkness. Melatonin helps regulate your circadian rhythm, which is the cycle of sleepiness and wakefulness in a 24-hour period.

Melatonin produced by the pineal gland impacts other areas of health. However, researchers still do not understand its full impact.3

Melatonin is a very effective antioxidant. It may protect neurons within the central nervous system from free radicals, such as nitric oxide or hydrogen peroxide. These chemicals are generated in active neural tissues. Free radicals may increase the risk of tissue damage and dysfunction, including the risk of medical problems like cancer and neurodegenerative disease.

 

Conditions Related to the Pineal Gland

The pineal gland and its melatonin production are central to the circadian rhythm disorders affecting sleep. For example, the pineal gland may exacerbate insomnia in delayed sleep phase syndrome. It also may have a role in seasonal affective disorder, sometimes known as winter depression. In addition, when the pineal gland is affected by tumors, the effects may lead to brain surgery.

Circadian Rhythm Disorders

These conditions occur when the synchrony between wakefulness and sleep patterns does not align with societal norms or the natural rhythm of light and darkness. Characterized by irregular bedtimes and awakenings, the affected person will experience insomnia and improperly timed sleepiness. The circadian sleep disorders include:

• Delayed sleep phase syndrome: Night owls who have difficulty getting to sleep and trouble waking early
• Advanced sleep phase syndrome: Characterized by early sleep onset and early morning awakening
• Free-running or non-24: Most often found in blind people without light perception, the timing of sleep may shift gradually over weeks or months
• Irregular sleep-wake rhythm: Shorter intervals of sleep over the 24-hour day rather than a prolonged sleep period overnight

How can sleep timing be disordered? Ultimately, this may depend on personal perspective, which is largely influenced by social context. One must be careful to avoid labeling normal variations of physiologic patterns as a disease.

Seasonal Affective Disorder (SAD)

With the prolonged darkness of night that occurs in the winter months within the northern hemisphere, seasonal affective disorder may ensue. Also known as winter depression, the condition may be associated with other symptoms, including reduced physical activity and weight gain.

Pineal Gland Tumors

Cancer may rarely affect the pineal gland. Less than 1% of brain tumors occur in the pineal gland, but 3%–8% of brain tumors in children are found here.4 Generally, pineal gland tumors occur more among young adults between 20 and 40 years of age. There are only a handful of tumors that may affect the pineal gland within the brain. There are only three types of true pineal cell tumors. These include:

• Pineocytoma: Slow-growing, often classified as a grade II tumor
• Pineoblastoma: Generally more aggressive, either classified as a grade III intermediate form or more malignant grade IV
• Mixed pineal tumor: Contains a combination of cell types, making a clean classification less possible

These tumors may grow large enough to obstruct the normal flow of the cerebrospinal fluid within the ventricles. It is estimated that 10%–20% of the pineal gland tumors may also spread via this medium, especially the more aggressive pineoblastoma variant. Fortunately, these cancers rarely metastasize elsewhere in the body.

Symptoms that develop with a pineal gland tumor may include:

• Impaired eye movements causing double vision
• Headache
• Nausea
• Vomiting

Other Conditions

Certain medications may affect the relay from the eye’s perception of light to the production of melatonin within the pineal gland. In particular, beta-blocking medications used to treat hypertension, tachycardia, and heart disease may interfere with the normal release of melatonin.5 Beta-blockers include Lopressor (metoprolol), Tenormin (atenolol), and Inderal (propranolol). If this significantly impacts sleep or health, a different medication may need to be used.

The pineal gland may become calcified in older individuals, lighting up on computed tomography (CT) scans due to its increased density and leading to the presence of “brain sand” on a pathological assessment of the tissue.6

 

Tests to Check the Pineal Gland

In most cases, testing to assess the pineal gland is not indicated. Melatonin levels can be measured in the saliva, blood, and urine without direct assessment of the pineal gland; however, this is mainly done in the context of research studies and not in clinical care. Given its size, some imaging techniques may provide limited data about the structure. In the context of pineal gland tumors, the following tests may be appropriate:

• CT scan
• Magnetic resonance imaging (MRI) scan
• Brain biopsy (removing a sample of tissue for further testing in a lab)

Further assessment of circadian disorders may require evaluation by a board-certified sleep specialist who will ask targeted questions further to understand the patterns and impacts of the problem.

Tracking of the circadian rhythm may be done longitudinally with sleep logs or actigraphy. Wearable technology, including common fitness trackers, may provide some of this biometric data. The sleep specialist will also direct appropriate interventions, including the potential use of melatonin supplementation or phototherapy, to optimize sleep and well-being.

 

How Pineal Gland Conditions Are Treated

Treatment for pineal gland conditions depends on the condition and the problems it is posing in a person’s life.

Circadian Rhythm Disorders

Treatment may be appropriate when circadian rhythm disorders are causing significant social and occupational dysfunction (including absenteeism from school or work). If someone’s irregular sleep patterns are not negatively affecting their life, medical help is not typically necessary.

Treatment can include light box therapy, melatonin supplements, and lifestyle changes. Some lifestyle changes that can help include reducing caffeine, maintaining a regular bedtime routine, avoiding naps, exercising, and not using devices close to bedtime.7

Seasonal Affective Disorder

Phototherapy may be helpful with the artificial application of light from a light box or light therapy glasses. The timing of the light is typically in the morning, but it is essential to follow the guidance of a medical professional.

Pineal Gland Tumors

If a pineal gland tumor is identified, treatment typically includes radiation. If pineoblastoma is present, the entire brain and spinal cord must receive radiation therapy. If the tumor has spread or if it regrows after radiation treatment, chemotherapy may be indicated.

In some cases, surgery may determine the tumor type by removing part of the tumor. If the flow of cerebrospinal fluid is blocked, leading to swelling within the brain, a shunt may be placed to ensure normal circulation beyond the tumor site.

 

Summary

The pineal gland produces melatonin, which is responsible for sleep-wake cycles, and likely has other effects in the body that researchers are still studying. It is located deep in the brain and is a small, pinecone-shaped structure about the size of a grain of rice.

Some conditions that can arise from pineal gland dysfunction are seasonal affective disorder and circadian rhythm disorders. Pineal glands can rarely develop cancerous tumors, which often do not metastasize and can be treated with radiation, chemotherapy, and sometimes surgery