Glands of the endocrine system
The endocrine system is a distinct organ system within the human body that’s responsible for the production and secretion of hormones. It is composed of a group of glands that secrete a wide range of hormones that produce their effects across the body .1 Hormones are chemical messengers that produce certain physiological responses. For example, insulin, a pancreatic hormone, regulates blood sugar levels. Hormones also regulate metabolism, reproduction, mood, and organ function.1
Endocrine glands are spread out within the body. From head to toe, they are as follows:
The hypothalamus is an endocrine gland located at the base of the brain.2 It is the communication point between the endocrine system and the nervous system. The hypothalamus releases hormones to the pituitary gland to control the body’s hormone release. The hypothalamus also controls body temperature, circadian rhythm, and sensations of hunger and thirst.3
- Pituitary Gland: The pituitary gland has a diverse range of functions to maintain the endocrine system. Upon receiving signals from the brain via the hypothalamus, it receives information on what hormones are needed in the body for the other glands to produce.1 The pituitary gland produces ACTH (stress hormone), growth hormone, oxytocin (hormone for childbirth and breast milk production), and others.4
- Pineal Gland: The pineal gland produces melatonin, a hormone that prepares the body for sleep.1
- Thyroid Gland: The thyroid gland produces the thyroid hormone. The thyroid hormone regulates the body’s metabolism and growth by controlling how cells use calories, regulating heart rate, regulating temperature, and slowing down or speeding up metabolism.5 The thyroid gland is implicated in hyperthyroidism (overactivity of the thyroid gland) and hypothyroidism (under-activity of the thyroid gland).1
- Parathyroid gland: The parathyroid gland is situated behind the thyroid gland and is responsible for controlling the body’s calcium and phosphorus levels.1
- Thymus Gland: The thymus gland has a significant role in the immune system as it produces T lymphocytes. T lymphocytes are white blood cells that fight infections such as viruses.1
- Adrenal Gland: The adrenal gland produces the hormones that are secreted in the “fight or flight” response: noradrenaline and adrenaline.1 When these adrenal hormones are secreted, it causes increased heart rate, constriction of the blood vessels, increased blood glucose levels, and pupil enlargement.6
- Pancreas: The pancreas is the largest endocrine gland in the human body. It is responsible for producing and secreting the enzymes that aid in the breakdown of food, such as insulin and glucagon.1 Insulin is produced by the pancreas’ beta cells to decrease the amount of sugar in the blood, while glucagon is produced by the pancreas alpha cells to increase the amount of sugar in the blood.7
- Ovaries: The ovaries are the female sex organs, but they are also endocrine glands, as they release hormones such as oestrogen, progesterone, and follicle-stimulating hormone that are necessary for female puberty, menstrual cycle regulation, and pregnancy.1,8
- Testes: The testes are the male sex organs, and like the ovaries, are also endocrine organs. The testes produce testosterone which aids in the growth of pubic and facial hair during puberty and the production of sperm.1
What are endocrine disorders?
Endocrine disorders are health conditions that alter the function of the endocrine system causing it to be unable to adequately produce hormones. As hormones are the chemical messengers of the body, alterations in hormone production pose serious effects on an individual’s growth, metabolism and nutrient levels due to the diverse functions of hormones within the body.9
Causes and risk factors of endocrine disorders
Due to the great range of endocrine disorders, the exact cause depends on the exact endocrine disorder. Factors such as tumours, hormone imbalances, and genetics cause most endocrine disorders.9 However, not all endocrine disorders have an exact cause identified. Endocrine disorders are usually divided into two distinct categories: endocrine disorders that are caused by hormone imbalance (too much or too little of a hormone) and endocrine disorders caused by the presence of tumours and other factors that can affect an organ.10
Risk factors of endocrine disorders include:
- Older age
- High blood cholesterol
- High blood sugar
- Presence of Tumour(s) 11
Types of endocrine disorders
Most common types of endocrine disorder
- Diabetes: Diabetes is one of the most known endocrine disorders. It is attributed to high blood glucose levels due to the pancreas’ inability to produce glucose or the body not being able to properly use glucose to control blood glucose levels.9
Diabetes is divided into two categories: Type I and Type II diabetes. Type I diabetes is usually diagnosed in childhood, while type II is typically diagnosed in adulthood.9 As a response to the insulin hormone imbalance, individuals with diabetes may experience extreme fatigue, increased hunger and thirst, and blurred vision.9 According to WebMD, in the US, diabetes is the most commonly diagnosed endocrine disorder.10
- Hyperthyroidism: Hyperthyroidism is an endocrine disorder in which the thyroid gland produces an increased amount of thyroid hormones.9 Hyperthyroidism is often caused by a pathological change in the thyroid, such as inflammation or Graves’ Disease (an immune disorder).9
- Hypothyroidism: Hypothyroidism is attributed to insufficient production of thyroid hormones by the thyroid gland. It is the most common thyroid condition and results in the slowing down of many essential body processes and functions.9
- Polycystic Ovary Syndrome (PCOS): Polycystic Ovary Syndrome is an endocrine disorder in which androgen hormone overproduction in women affects the development of the eggs. This can manifest in women having irregular periods due to problems with the release of eggs from the ovaries.10
Signs and symptoms of endocrine disorders
The signs and symptoms of endocrine disorders are unique to each condition and the endocrine gland that is affected by the disorder. However, the most common signs and symptoms of endocrine disorders include mood swings, weakness, unexplainable weight changes, and changes in blood sugar and cholesterol levels.12 Ultimately, the signs and symptoms depend on the endocrine gland affected; for example, an individual who has a thyroid disorder will experience changes to their metabolism and heart rate.9 On the other hand, an individual who has an adrenal gland disorder will experience changes in their energy levels and skin changes.9
Diagnosis of endocrine disorders
Due to the wide range of differences in symptoms and clinical presentations of endocrine disorders, several different diagnostic methods may be used by medical professionals to diagnose the condition. There can also be an overlap of symptoms between different endocrine disorders due to the complex connections between each gland and hormone type in the endocrine system. Medical professionals may use:
- Urine tests
- MRI, PET, CT
- Blood tests
- Genetic Tests 9,11-12
These diagnostic methods aim to look for certain proteins or hormones within the urine, blood, or within the organ to check for a hormone imbalance or other pathological conditions that are associated with a specific endocrine disorder.9-11 Imaging tests can be used to assess whether there is a tumour or other lesion that is causing the endocrine disorder.10 Genetic tests can be used to identify a genetic trait that predisposes an individual to a specific endocrine disorder.
Treatment for endocrine disorders
Treatment for endocrine disorders can be difficult as restoring a hormone balance of one hormone can potentially cause an imbalance of another hormone due to intricate connections within the endocrine system.10 However, hormone replacement therapy can be used to treat endocrine diseases if inadequate or absent hormone production is the cause of the disorder.11 Endocrine disorders in which the hormone level is too high, patients can take medications that lower the hormone’s levels to restore its balance. In endocrine disorders caused by a tumour or lesion, surgery and radiotherapy are typically used to remove or shrink the tumour or lesion, respectively. Treatment also requires doctors and other medical professionals to constantly track hormonal levels to prevent adverse effects on the rest of the endocrine system and to maintain balance.10
When to see a doctor
Due to the wide range of symptoms that are associated with endocrine disorders, it can be very difficult to identify when you suspect you may have an endocrine disorder. If you experience any unusual symptoms, such as sudden irritability, fatigue, unexplained weight changes, hair loss, missed periods, and more, you should contact a doctor.9-11 These symptoms are typically general to several endocrine disorders and other non-endocrine disorders.9
The endocrine system is an organ system that produces and secretes hormones. Hormones are chemical messengers that circulate in the body to produce various physiological effects. Each endocrine gland produces and secretes a specific hormone for a specific function. Endocrine glands include the hypothalamus, thyroid, adrenal gland, pancreas, ovaries, and testes.1-3 Endocrine disorders are conditions where hormone imbalances within the endocrine system manifest into visible symptoms such as weight changes, skin changes, and energy changes.9 The most common endocrine disorders include diabetes, thyroid disorders, and sexual endocrine disorders. It can be difficult to diagnose endocrine disorders due to symptom overlap; however, diagnostic tests, including imaging tests, blood tests, and urine tests, can help ease the burden.11 If you think you may have an endocrine disorder due to sudden changes to your health, you should contact a doctor. Endocrine disorders can impact one’s daily health and can potentially be life-threatening.9
- Brody B. The Endocrine System and Glands of the Human Body [internet]. 2021 May 20 [cited 2022 July 27]. Available from: https://www.webmd.com/diabetes/endocrine-system-facts.
- Cleveland Clinic. Hypothalamus [internet]. 2022 March 16 [cited 2022 July 27]. Available from: https://my.clevelandclinic.org/health/articles/22566-hypothalamus.
- Brennan D. What to Know About the Hypothalamus [internet]. 2021 June 20 [cited 2022 July 27]. Available from: https://www.webmd.com/brain/what-to-know-about-hypothalamus
- Cleveland Clinic. Pituitary Gland [internet]. 2022 April 04 [cited 2022 July 27]. Available from: https://my.clevelandclinic.org/health/body/21459-pituitary-gland.
- Cleveland Clinic. Thyroid Gland [internet]. 2022 February 15 [cited 2022 July 27]. Available from: https://my.clevelandclinic.org/health/articles/22391-thyroid-hormone.
- You and your Hormones. Adrenaline [internet]. 2018 January [cited 2022 July 27]. Available from: https://www.yourhormones.info/hormones/adrenaline/.
- Cleveland Clinic. Glucagon [internet]. 2022 March 01 [cited 2022 July 27]. Available from: https://my.clevelandclinic.org/health/articles/22283-glucagon
- Cleveland Clinic. Ovaries [internet]. 2022 May 13 [cited 2022 July 27]. Available from: https://my.clevelandclinic.org/health/body/22999-ovaries
- Wood K. Kandola A. What to know about endocrine disorders [internet]. 2021 October 24 [cited 2022 July 27]. Available from: https://www.medicalnewstoday.com/articles/endocrine-disorders
- Miller K. Dansinger M. Endocrine Disorders [internet]. 2021 August 19 [cited 2022 July 27]. Available from: https://www.webmd.com/diabetes/endocrine-system-disorders
- Yashoda Hospitals. How to diagnose and treat Endocrine Disorders [internet]. 2020 May 06 [cited 2022 July 27]. Available from: https://www.yashodahospitals.com/blog/endocrine-disorders-symptoms-causes-diagnosis-treatments/
- Tampa General Hospital. Endocrine Disorders [internet]. 2022. [cited 2022 July 27]. Available from: https://www.tgh.org/institutes-and-services/conditions/endocrine-disorder