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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

Video Transcript

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:

Video Transcript

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 - 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 - 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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