Pineal Gland Location, Function, and Conditions
송과선 위치,기능 및 상태
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:
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.
The pineal gland alters the production of melatonin based on the amount of light perceived by the eyes. Due to its ability to respond to light perception, the pineal gland has been called the “third eye” of the body.
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)