What is the Pineal Gland and What is Its Function?

Published May 12th, 2022 by Erik Rivera
Fact Checked by
Jacqueline Hensler
Medically Reviewed:
Chris Riley

The pineal gland is a small, cone-shaped gland located in your brain. It is responsible for producing the hormone melatonin, which helps regulate the body's circadian rhythm, also known as your sleep-wake cycle.

The pineal gland can also be affected by certain medical conditions or problems, some of which can have severe consequences.

In this article, we will discuss the pineal gland and its function in detail.

We will also look at how doctors diagnose problems with the pineal gland, and what treatments are available if a problem is found.

What is the pineal gland?

The pineal gland, also called the pineal body, conarium, or epiphysis cerebri, is a small, pinecone-shaped endocrine gland that is located in the brain.

The average pineal gland is as small as a grain of rice.

The pineal gland produces melatonin, a hormone derived from the amino acid tryptophan that helps regulate the sleep-wake cycle.

pineal gland

Melatonin is also thought to be involved in the production of certain hormones, such as serotonin although doctors and scientists are still uncertain about all of its functions.

The pineal gland knows when to produce more melatonin based on the amount of light received by your eyes.

It is located in a part of your brain known as the epithalamus, which is in the back of your brain near the brain stem.

It is sometimes referred to as the third eye by spiritual practitioners.

What is the function of the pineal gland?

There are several known functions of the pineal gland and they include:

Melatonin production

The pineal gland helps to regulate your circadian rhythm by producing melatonin which is a hormone that makes you feel sleepy.

It is produced in response to darkness and regulates your sleep-wake cycle. The pineal gland also converts serotonin to melatonin, which it then excretes.

When you are exposed to light, your pineal gland slows down or stops producing melatonin.

Besides sleep, the production of melatonin has some other functions that are not fully understood.

In some animals, an increase in melatonin can cause a decrease in the amount of a hormone that aids in reproductive functions.

It is also thought that melatonin may also play a role in the seasonal reproductive habits of certain animals.

In winter months when there is less light and the pineal gland in animals produces more melatonin, this may lead to less fertility for these animals.

More research is needed on the subject to see if it has any consequences on humans.

Melatonin also is an antioxidant which means it can help to protect cells from damage caused by free radicals.

Free radicals are substances that can damage cells and contribute to the development of conditions like cancer and neurodegenerative disorders.

It is theorized that melatonin may help protect your brain cells due to these antioxidant properties.


One study has shown that a decrease in melatonin may increase the risk for certain types of cancers in rats while another study has shown that it may help fight cancer.

More research is needed on both subjects to draw any firm conclusions on the role of melatonin in treating cancer.

Heart health

One review found that melatonin may help with cardiovascular health by reducing your blood pressure.

It may even help treat cardiovascular disease, also called heart disease, although more research is also needed before drawing any conclusions.

Bone health

Studies on mice have concluded that melatonin may also help with bone deposition, which is the process of building new bone material.

More research on the human pineal gland needs to be conducted first to verify these conclusions.

Pituitary gland regulation

Studies that have been conducted on rodents with their pineal gland removed were found to have higher levels of certain hormones.

Melatonin was also administered to determine if the lack of it was the cause for these rises in hormone levels; however, the hormone levels did not fall which suggests the pineal gland helps regulate the pituitary gland.

Due to the studies being on rodents, more research is needed.

Mood disorders

A study was conducted that concluded that there is a correlation between the size of the pineal gland and mood disorders.

Those with smaller pineal glands were more likely to suffer from schizophrenia and other mood disorders.

More extensive research is needed to draw any conclusions from the study and the significance of melatonin on mood disorders.

Female hormones

An older study concluded that light exposure and melatonin levels may help regulate a woman's menstrual cycle.

Women who had low levels of melatonin were more likely to have irregular menstrual cycles. More extensive and current research is needed to draw any conclusions.

What medical conditions or problems can occur to the pineal gland or are linked to it?

Several medical conditions can occur due to your pineal gland. Although rare, it is possible to get a tumor on your pineal gland too.

Conditions linked to or caused by the pineal gland include:

Circadian rhythm sleep disorders

There are a number of disorders that can disrupt your circadian rhythm. Pineal gland disorders can cause problems with this daily cycle. These disorders include

  • Delayed sleep phase syndrome, which is when you find it hard to fall asleep at night and wake up in the morning
  • Advanced sleep phase syndrome, which is when you fall asleep really early and wake up very early too
  • Free running, also called non-24 hour sleep-wake disorder, is often found in blind people and it is when your sleep cycle shifts and does not follow the conventional 24-hour cycle
  • Irregular sleep-wake rhythm, this occurs when you fall asleep for shorter periods throughout the day and not for one long period at night

Seasonal affective disorder (SAD)

Seasonal affective disorder is a type of depression that occurs during certain seasons, typically winter.

It is linked to the pineal gland because it is thought that the shorter days and lack of sunlight may disrupt your circadian rhythm and pineal gland function, which can lead to seasonal affective disorder.


Pineal gland tumors can occur but are very rare. These tumors can contain one of three types of pineal cells:

  • Pineocytoma cells, which are grade II cancer cells
  • Pineoblastoma cells, which are grade III or grade IV cancer cells
  • Mixed pineal tumor, which is when the tumor contains multiple types of cancer cells

Symptoms of a pineal tumor include:

  • Headaches
  • Double vision
  • Vomiting
  • Nausea
  • Mental deterioration
  • Dementia-like behavior

These symptoms all occur due to pressure on the brain, which is called hydrocephalus.

Treatment for a tumor on your pineal gland usually consists of radiation and possibly chemotherapy. Surgery may also be an option.

Medication interactions

Beta-blocking medications are most often used to treat heart disease, high blood pressure, and tachycardia, which is when you have a high heart rate and can all cause a disruption in the release of melatonin from your pineal gland.

If this happens and it affects your sleep, your doctor may switch medications.


Calcification is the buildup of calcium deposits on your pineal gland, which is more common as you age, and can be seen on a brain scan and it is uncertain whether it affects sleep patterns.

It also causes "brain sand," which are calcified objects on your pineal gland and other parts of your brain.

From around the web: pineal gland

Reddit - Pineal Gland

Pinterest - Pineal Gland

How do doctors diagnose problems with the pineal gland?

Your doctor can diagnose pineal gland problems using a number of different tests, which include:

Measuring your melatonin levels

There are saliva, blood, and urine tests available to measure melatonin levels.

Computer tomography scan (CT scan)

CT scans use X-rays to take cross-sectional pictures of your brain which can help doctors see if there are any tumors on your pineal gland or calcification.

Magnetic resonance imaging scan (MRI scan)

MRI scans use magnets to take pictures of your brain but they provide more detailed images.

If you are having trouble sleeping, your doctor may also suggest you visit a board-certified sleep specialist who can help you with your sleeping troubles.


The pineal gland is a small endocrine gland in your brain that produces melatonin, which helps regulate your sleep-wake cycle.

Conditions linked to or caused by the pineal gland include circadian rhythm disorders, seasonal affective disorder, pineal tumors, and medication interactions among others.

Your doctor can diagnose pineal gland problems using tests like measuring melatonin levels, CT scans, and MRI scans and if you are having difficulty sleeping due to low melatonin levels, you may be referred to a sleep specialist.

If you have any more questions or think you may have a problem with your pineal gland or melatonin levels, please talk to your doctor or health care provider.

References and sources:

Dove Press

Wiley Online Library


SAGE journals

American Brain Tumors Association

Oxford Academic


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