Learn About the Function of the Pineal Gland

Pineal Gland
The pineal gland secretes the hormone melatonin which controls the body's biological clock. It is a small gland situated deep within the brain, just below the back of the corpus callosum. Credit: PASIEKA/Science Photo Library/Getty Images

What Is the Pineal Gland?

The pineal gland is a small, pinecone shaped gland of the endocrine system. A structure of the diencephalon of the brain, the pineal gland produces the hormone melatonin. Melatonin influences sexual development and sleep-wake cycles. The pineal gland is composed of cells called pinealocytes and cells of the nervous system called glial cells. The pineal gland connects the endocrine system with the nervous system in that it converts nerve signals from the sympathetic system of the peripheral nervous system into hormone signals.

Over time, calcium deposits build-up in the pineal and its accumulation can lead to calcification in the elderly.


The pineal gland is involved in several functions of the body including:

  • Secretion of the Hormone Melatonin
  • Regulation of Endocrine Functions
  • Conversion of Nervous System Signals to Endocrine Signals
  • Causes Feeling of Sleepiness
  • Influences Sexual Development
  • Influences Immune System Function
  • Antioxidant Activity


Directionally the pineal gland is situated between the cerebral hemispheres and attached to the third ventricle. It is located in the center of the brain.

Pineal Gland and Melatonin

Melatonin is produced within the pineal gland and synthesized from the neurotransmitter serotonin. It is secreted into cerbrospinal fluid of the third ventricle and is directed from there into the blood. Upon entering the bloodstream, melatonin can be circulated throughout the body. Melatonin is also produced by other body cells and organs including retinal cells, white blood cells, gonads, and skin.

Melatonin production is vital to the regulation of sleep-wake cycles (circadian rhythm) and its production is determined by light and dark detection. The retina sends signals about light and dark detection to an area of the brain called the hypothalamus. These signals are eventually relayed to the pineal gland.

The more light detected, the less melatonin produced and released into the blood. Melatonin levels are at their highest during the night and this promotes changes in the body that help us to sleep. Low levels of melatonin during daylight hours help us to stay awake. Melatonin has been used in the treatment of sleep related disorders including jet lag and shift-work sleep disorder. In both of these cases, a person's circadian rhythm is disrupted either due to travel across multiple time zones or due to working night shifts or rotating shifts. Melatonin has also been used in the treatment of insomnia and depressive disorder.

Melatonin influences the development of reproductive system structures as well. It inhibits the release of certain reproductive hormones from the pituitary gland that affect male and female reproductive organs. These pituitary hormones, known as gonadotropins, stimulate gonads to release sex hormones. Melatonin therefore regulates sexual development. In animals, melatonin plays a role in regulating mating seasons.

Pineal Gland Dysfunction

Should the pineal gland begin to function abnormally, a number of problems may result. If the pineal gland is not able to produce sufficient amounts of melatonin, a person could experience insomnia, anxiety, low thyroid hormone production (hypothyroidism), menopause symptoms, or intestinal hyperactivity.

If the pineal gland produces too much melatonin, a person could experience low blood pressure, abnormal function of the adrenal and thyroid glands, or Seasonal Affective Disorder (SAD). SAD is a depressive disorder that some individuals experience during the winter months, when sunlight is minimal.

Pineal Gland Images

Divisions of the Brain

  • Forebrain - encompasses the cerebral cortex and brain lobes.
  • Midbrain - connects the forebrain to the hindbrain.
  • Hindbrain - regulates autonomic functions and coordinates movement.


  • "pineal gland". Encyclopædia Britannica. Encyclopædia Britannica Online. Encyclopædia Britannica Inc., 2016. Web. 26 Jan. 2016 http://www.britannica.com/science/pineal-gland
  • "melatonin". Encyclopædia Britannica. Encyclopædia Britannica Online. Encyclopædia Britannica Inc., 2016. Web. 26 Jan. 2016 http://www.britannica.com/science/melatonin
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    Bailey, Regina. "Learn About the Function of the Pineal Gland." ThoughtCo, Sep. 14, 2017, thoughtco.com/pineal-gland-anatomy-373225. Bailey, Regina. (2017, September 14). Learn About the Function of the Pineal Gland. Retrieved from https://www.thoughtco.com/pineal-gland-anatomy-373225 Bailey, Regina. "Learn About the Function of the Pineal Gland." ThoughtCo. https://www.thoughtco.com/pineal-gland-anatomy-373225 (accessed February 18, 2018).