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Endocrine glands

Endocrine glands release (secrete) hormones into the bloodstream.

The endocrine glands include:

  • Adrenal
  • Hypothalamus
  • Islets of Langerhans in the pancreas
  • Ovaries
  • Parathyroid
  • Pineal
  • Pituitary
  • Testes
  • Thyroid

Endocrine glands - Animation

The endocrine system is primarily composed of glands that produce chemical messengers called hormones. Glands of the endocrine system include the pituitary gland, the thyroid gland, the parathyroid glands, the thymus, and the adrenal glands. Other glands are also included within the endocrine system since they contain endocrine tissue that secretes hormones. These include the pancreas, ovaries and testes. The endocrine and nervous systems work very closely together. The brain continuously sends instructions to the endocrine system, and in return receives feedback from the endocrine glands. Because of this intimate relationship, the nervous and endocrine systems are referred to as the neuroendocrine system. The hypothalamus is known as the master switchboard because it's the part of the brain that controls the endocrine system. The pituitary gland, which hangs by a thin stalk from the hypothalamus, is called the master gland of the body because it regulates the activity of the endocrine glands. The hypothalamus detects the rising level of the target organ's hormones then sends either hormonal or electrical messages to the pituitary gland. In response, the pituitary gland releases hormones, which travel through the bloodstream to a target endocrine gland, instructing it to stop producing its hormones. Here's how the endocrine system keeps itself in check eventually, the hypothalamus detects the rising level of the target organ's hormones, and sends a message to the pituitary gland. The pituitary gland then stops releasing certain hormones, causing the target organ to stop producing its hormones. The endocrine system constantly adjusts hormone levels so that the body can function normally. This process is called homeostasis.

Information

Hypersecretion is when an excess of one or more hormone is secreted from a gland. Hyposecretion is when the amount of hormones that are released is too low.

There are many types of disorders that can result when too much or too little of a hormone is released.

Disorders that may be associated with abnormal hormone product from a particular gland include:

Adrenal:

Pancreas:

Parathyroid:

  • Low blood calcium level
  • Tetany (abnormal cramping of muscles)
  • Renal calculi (kidney stones)
  • Excessive loss of minerals from bone (osteoporosis)

Pituitary:

Pituitary gland - Animation

The pituitary gland is often referred to as the master gland of the body, since it regulates many activities of other endocrine glands. Located above the pituitary gland is the hypothalamus. The hypothalamus decides which hormones the pituitary should release by sending it either hormonal or electrical messages. In response to hormonal messages from the hypothalamus, the pituitary gland releases the following hormones. GH (growth hormone) - increases size of muscle and bone. THS (thyroid stimulating hormone) - stimulates the thyroid gland to release T3 and T4 to stimulate metabolism in other cells throughout the body. FSH (follicle stimulating hormone) - stimulates ovarian follicle production in women; stimulates sperm production in men. LH (luteinizing hormone) - stimulates ovaries to produce estrogen in women; stimulates sperm production in men. Prolactin - stimulates breast tissue in nursing mothers to produce milk. ACTH (adrenocorticotropic hormone) - causes the adrenal glands to produce important substances that have properties similar to steroids. In response to electrical messages from the hypothalamus, the pituitary gland releases the following hormones. ADH (antidiuretic hormone) - stimulates the kidneys to reabsorb fluid and produce less urine; Oxytocin - initiates labor, uterine contractions, and milk ejection in mothers.

Testes and ovaries:

  • Lack of sex development (unclear genitalia)

Thyroid:

Review Date: 5/12/2023

Reviewed By

Sandeep K. Dhaliwal, MD, board-certified in Diabetes, Endocrinology, and Metabolism, Springfield, VA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

References

Barrett EJ. Organization of endocrine control. In: Boron WF, Boulpaep EL, eds. Medical Physiology. 3rd ed. Philadelphia, PA: Elsevier; 2017:chap 47.

Melmed S, Auchus RJ, Goldfine AB, et al. Principles of endocrinology. In: Melmed S, Auchus RJ, Goldfine AB, Koenig RJ, Rosen CJ, eds. Williams Textbook of Endocrinology. 14th ed. Philadelphia, PA: Elsevier; 2020:chap 1.

Newell-Price JDC, Gibb FW. Endocrinology. In: Penman ID, Ralston SH, Strachan MWJ, Hobson RP, eds. Davidson's Principles and Practice of Medicine. 24th ed. Philadelphia, PA: Elsevier; 2023:chap 20.

Disclaimer

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. No warranty of any kind, either expressed or implied, is made as to the accuracy, reliability, timeliness, or correctness of any translations made by a third-party service of the information provided herein into any other language. © 1997- A.D.A.M., a business unit of Ebix, Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

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Endocrine glands

Endocrine glands

Animation

Pituitary gland

Pituitary gland

Animation

Endocrine glands - Illustration Thumbnail

Endocrine glands

Endocrine glands release hormones (chemical messengers) into the bloodstream to be transported to various organs and tissues throughout the body. For instance, the pancreas secretes insulin, which allows the body to regulate levels of sugar in the blood. The thyroid gets instructions from the pituitary to secrete hormones which determine the rate of metabolism in the body (the more hormone in the bloodstream, the faster the chemical activity; the less hormone, the slower the activity).

Illustration

Brain-thyroid link - Illustration Thumbnail

Brain-thyroid link

Although the thyroid gland releases the hormones which govern growth and metabolism, the brain (the pituitary and the hypothalamus) manages the release and the balance of the amount of hormones circulated.

Illustration

 
Endocrine glands

Endocrine glands

Animation

Pituitary gland

Pituitary gland

Animation

 
Endocrine glands - Illustration Thumbnail

Endocrine glands

Endocrine glands release hormones (chemical messengers) into the bloodstream to be transported to various organs and tissues throughout the body. For instance, the pancreas secretes insulin, which allows the body to regulate levels of sugar in the blood. The thyroid gets instructions from the pituitary to secrete hormones which determine the rate of metabolism in the body (the more hormone in the bloodstream, the faster the chemical activity; the less hormone, the slower the activity).

Illustration

Brain-thyroid link - Illustration Thumbnail

Brain-thyroid link

Although the thyroid gland releases the hormones which govern growth and metabolism, the brain (the pituitary and the hypothalamus) manages the release and the balance of the amount of hormones circulated.

Illustration

 
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Endocrine glands - Animation

The glands that make up the endocrine system produce chemical messengers called hormones that travel through the blood to other parts of the body.

Important endocrine glands include the pituitary, thyroid, parathyroid, thymus, and adrenal glands.

There are other glands that contain endocrine tissue and secrete hormones, including the pancreas, ovaries, and testes.

The endocrine and nervous systems work closely together. The brain sends instructions to the endocrine system. In return, it gets constant feedback from the glands.

The two systems together are called the neuro endocrine system.

The hypothalamus is the master switchboard. It's the part of the brain that controls the endocrine system. That pea-sized structure hanging below it is the pituitary gland. It's called the master gland because it regulates the activity of the glands.

The hypothalamus sends either hormonal or electrical messages to the pituitary gland. In turn, it releases hormones that carry signals to other glands.

The system maintains its own balance. When the hypothalamus detects the rising level of hormones from a target organ, It sends a message to the pituitary to stop releasing certain hormones. When the pituitary stops, it causes the target organ to stop producing its hormones.

The constant adjustment of hormone levels lets the body function normally.

This process is called homeostasis.

 

Pituitary gland - Animation

The pituitary gland lies deep inside the head. It's often called the "master gland" because it controls many of the things other glands do.

Just above the pituitary is the hypothalamus. It sends hormonal or electrical signals to the pituitary. These determine which hormones the pituitary will release.

For example, the hypothalamus might send a hormone called GHRH, or growth hormone releasing hormone. That would trigger the pituitary's release of growth hormone, which affects the size of both muscle and bone.

How important is this? Not getting enough during childhood can cause pituitary dwarfism. Getting too much can cause the opposite condition called gigantism. In a body that has already matured, too much growth hormone can cause acromegaly. With this condition, facial features become rough and course; the voice becomes deeper; and hand, foot, and skull size expand.

A different hormonal command from the hypothalamus might trigger the release of thyroid stimulating hormone or TSH. TSH causes the thyroid to release two hormones called T3 and T4 that stimulate metabolism in other cells throughout the body.

The pituitary can also release a hormone called antidiuretic hormone, or ADH. It's produced in the hypothalamus and stored in the pituitary. ADH affects the production of urine. When it's released, the kidneys absorb more of the fluid that passes through them. That means less urine is produced.

Alcohol inhibits the release of ADH, so drinking alcoholic beverages results in more urine production.

The pituitary gland produces other hormones that control other bodily functions and processes.

For instance, follicle stimulating hormone, or FSH, and luteinizing hormone, or LH, are hormones that affect the ovaries and egg production in women. In men, they affect the testes and sperm production.

Prolactin is a hormone that affects breast tissue in nursing mothers.

ACTH or adrenocorticotrophic hormone causes the adrenal glands to produce important substances similar to steroids.

Growth, puberty, baldness, even sensations like hunger and thirst, are just a few of the processes that are influenced by the endocrine system.

 

Endocrine glands - Animation

The glands that make up the endocrine system produce chemical messengers called hormones that travel through the blood to other parts of the body.

Important endocrine glands include the pituitary, thyroid, parathyroid, thymus, and adrenal glands.

There are other glands that contain endocrine tissue and secrete hormones, including the pancreas, ovaries, and testes.

The endocrine and nervous systems work closely together. The brain sends instructions to the endocrine system. In return, it gets constant feedback from the glands.

The two systems together are called the neuro endocrine system.

The hypothalamus is the master switchboard. It's the part of the brain that controls the endocrine system. That pea-sized structure hanging below it is the pituitary gland. It's called the master gland because it regulates the activity of the glands.

The hypothalamus sends either hormonal or electrical messages to the pituitary gland. In turn, it releases hormones that carry signals to other glands.

The system maintains its own balance. When the hypothalamus detects the rising level of hormones from a target organ, It sends a message to the pituitary to stop releasing certain hormones. When the pituitary stops, it causes the target organ to stop producing its hormones.

The constant adjustment of hormone levels lets the body function normally.

This process is called homeostasis.

 

Pituitary gland - Animation

The pituitary gland lies deep inside the head. It's often called the "master gland" because it controls many of the things other glands do.

Just above the pituitary is the hypothalamus. It sends hormonal or electrical signals to the pituitary. These determine which hormones the pituitary will release.

For example, the hypothalamus might send a hormone called GHRH, or growth hormone releasing hormone. That would trigger the pituitary's release of growth hormone, which affects the size of both muscle and bone.

How important is this? Not getting enough during childhood can cause pituitary dwarfism. Getting too much can cause the opposite condition called gigantism. In a body that has already matured, too much growth hormone can cause acromegaly. With this condition, facial features become rough and course; the voice becomes deeper; and hand, foot, and skull size expand.

A different hormonal command from the hypothalamus might trigger the release of thyroid stimulating hormone or TSH. TSH causes the thyroid to release two hormones called T3 and T4 that stimulate metabolism in other cells throughout the body.

The pituitary can also release a hormone called antidiuretic hormone, or ADH. It's produced in the hypothalamus and stored in the pituitary. ADH affects the production of urine. When it's released, the kidneys absorb more of the fluid that passes through them. That means less urine is produced.

Alcohol inhibits the release of ADH, so drinking alcoholic beverages results in more urine production.

The pituitary gland produces other hormones that control other bodily functions and processes.

For instance, follicle stimulating hormone, or FSH, and luteinizing hormone, or LH, are hormones that affect the ovaries and egg production in women. In men, they affect the testes and sperm production.

Prolactin is a hormone that affects breast tissue in nursing mothers.

ACTH or adrenocorticotrophic hormone causes the adrenal glands to produce important substances similar to steroids.

Growth, puberty, baldness, even sensations like hunger and thirst, are just a few of the processes that are influenced by the endocrine system.

 
 
 
 

 

 
 
 
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