The Endocrine System and Its Glands

Written by Dr. Ahmed Zayed
Endocrine System

Introduction

There are many systems within the human body that regulate certain functions to ensure we are able to get up in the morning, get through the day and steer clear of disease. Each system and part of the body has its own vital part to play in the maintenance of our wellbeing. When we fall ill, we often concern ourselves about major organs in the body, such as the lungs and heart, or perhaps the stomach, and tend to overlook other parts of the human body that also plays essential roles and, when struck by disease, can lead to symptoms that make it seems like the vital organs are acting out.

The brain regulates all functions of the human body and it allows us to see, hear, taste, speak and, of course, process information. The heart pumps blood throughout the body, the gastrointestinal tract processes food and allows us to absorb nutrients from food sources. While the general functions of these organs are well-known by the majority of the human population, people are not always as educated about the different systems that are involved in the wellbeing of the human body.

There are 11 different systems within the human body, each playing a role in helping various functions of the body work efficiently. These systems include the circulatory system, the digestive system, the immune system, the lymphatic system, the muscular system, the nervous system, reproductive system, respiratory system, skeletal system, skin and, of course, the urinary system. In addition to these, there is also one particular system that we would like to focus on in this guide – the endocrine system. This system is particularly important for the production of hormones and, without a working endocrine system, we are prone to developing numerous health concerns and symptoms that may be unpleasant.

What Is The Endocrine System?

The endocrine system has important parts to play in the human body. This system consists of glands that can be observed throughout the human body, from the head all the way down towards the genital region of the body. The purpose of these glands that are part of the endocrine system is to produce a large variety of hormones. In turn, these hormones are responsible for numerous functions in the body, such as to aid in digestion. The hormones that are produced by these glands also form part of the endocrine system.

Endocirine System Info

The glands that are part of the human body’s endocrine system are primarily controlled by the nervous system. The nervous system stimulates these glands, which then causes them to release certain hormones in certain doses. In addition to the nervous system stimulating the glands to release hormones, certain chemical receptors that are found in the blood circulatory system can also cause hormones to be released from these glands. It is also important to understand that some hormones that circulates through the bloodstream may also cause a reaction that leads to the release of hormones by another gland.

Glands and the hormones they release, or the endocrine system, has a vital part to play in the regulation of organs in the body, including the heart, the brain, the reproductive organs and more. By regulating organ functionality, the endocrine system contributes to the homeostasis of the human body, which means it helps to create a balance between all hormones and their functions to ensure everything in the body works at an optimum level, without any particular parts working too hard to too poorly, which may result in the development of certain issues.

According to Medline Plus[1], the hormones that are produced and released into the body by the glands that are part of the endocrine system affects many different functions of various body parts. The affected functions include the patient’s development, as well as their growth, their metabolism function, sexual and reproductive function. In addition to these affected functions, it is also important to note that these hormones can have a major impact on a patient’s overall mood.

In this report, we are going to explore each particular gland that is part of the endocrine system in the human body in detail. We are going to look at where it is located, what hormones it produces, what hormones it is affected by and, of course, what purposes the hormones produced by each gland serves.

Which Are The Glands That Form Part Of Endocrine System?

Parts of Endocrine System

To thoroughly understand how the endocrine system works, it is important to dig deeper into the topic than to just mention that the endocrine system refers to the glands in the human body that produce hormones. Each of these glands produces different types of hormones; thus playing a unique role in the regulation of organs and other vital parts of the human body. For this reason, we would like to start this report by looking at the particular glands that are part of the endocrine system, and discuss the hormones they produce, as well as discuss their particular purposes in the body.

The Hypothalamus

Before we can discuss the various hormone producing glands that form the endocrine system in the body, it is important to take a few moments to first look at the hypothalamus. This is, after all, the part of the human body that controls the particular functions that the endocrine system needs to execute in order for a proper homeostasis between all organs, systems and parts of the body. Healthline[2] explains that the hypothalamus is a particularly small part of the brain, yet this particular region plays a very important part in regulating the entire body’s endocrine system, as well as numerous psychological and physiological processes. This includes behavioral functions, as well as autonomic functions, which includes any involuntary actions, as well as unconscious actions that the body performs. The hypothalamus also has a part in the development and growth of the human bod, as well as the body’s metabolism function.

Considering the details we have discussed above, it is quite easy to notice that the hypothalamus can be thought of as both the beginning and also the “center point” of the endocrine system. This particular system continuously monitors the entire body, including the total body weight of a patient, their blood pressure levels, their body temperature, electrolyte levels and more. These values are provided to the hypothalamus as inputs, which then helps this part of the endocrine system calculate particular changes that can be made in the body to bring about a better homeostasis.

It is also important to note that the hypothalamus works on a “set point” system, which means it knows how much the patient should weight, the most appropriate level of electrolytes for their body and details about the other particular aspects it monitors continuously. When this part of the endocrine system detects a change in any aspect that it monitors, it will act accordingly to help restore a healthy balance.

The hypothalamus creates numerous types of hormones, which, in turn, helps to regulate the function of other glands in the body and to increase or decrease the level of hormones that are being excreted by these glands. Small vessels, known as capillaries, carries the hormones that the hypothalamus produces towards the blood circulatory system, which then delivers the hormones to the first gland found after the hypothalamus, which is the pituitary gland. Let’s take a closer look at the particular hormones that the hypothalamus can create and send to the pituitary gland.

Hypothalamus
  • Thyrotropin-Releasing Hormone – According to You And Your Hormones[3], thyrotropin-releasing hormones are responsible for regulating the activity of the thyroid gland in the human body. It is often referred to as TRH. This particular hormone is also a significantly small type of hormone. This type of hormone is produced by the paraventricular nucleus, a cluster of nerve cells found in the hypothalamus.
  • Gonadotropin-Releasing Hormone – This particular type of hormone is involved in the reproductive axis, which refers to the connection the brain and the reproductive system, including the patient’s reproductive organs. When the hypothalamus secretes gonadotropin-releasing hormones[4], a reaction occurs that causes the release of luteinizing hormone-releasing hormones. The pituitary gland then reacts to the newly secreted hormones and releases two types of other hormones into the blood circulatory system of the body. These two hormones include follicle-stimulating hormones and luteinizing hormones (more on these hormones later in this report).
  • Growth Hormone-Releasing Hormone – The growth hormone-releasing hormone[5] is produced by cells in the hypothalamus. The substance is then released into the bloodstream, where it travels towards the anterior pituitary gland. When the hormone reaches the anterior pituitary gland, it causes the production and release of, as the name suggests, growth hormones, into the body.
  • Corticotrophin-Releasing Hormone – This particular hormone has an important part to play in regulating the stress response of the body. The particular factor that corticotrophin-releasing hormone[6] is responsible for is the hypothalamic-pituitary-adrenal axis. When the hormone reaches the pituitary gland, it causes the release of the adrenocorticotropic hormone, which is later turned into another hormone that is often associated with stress, known as cortisol.
  • Somatostatin – Somatostatin[7] is another hormone produced in the hypothalamus. The purpose of this particular hormone is to inhibit the production of certain hormones in the body, which activates when that particular hormone is not needed, yet produced. In addition, Somatostatin also helps to prevent cells from reproducing unnaturally. It is important to note that Somatostatin acts as a type of neurotransmitter. This hormone also plays a part in the human body’s gastrointestinal tract.
  • Dopamine – This hormone is actually one of the more popular types of hormones in the human body. Almost everyone has at least heard the term “dopamine” before. According to Psychology Today[8], dopamine is a particular hormone that assists with the regulation of the pleasure and reward functions of the human brain. Furthermore, dopamine is also involved in the emotional responses of people, as well as in the regulation of their movement towards a response.
  • Oxytocin – Oxytocin is a particular hormone that acts as a neurotransmitter in the body. Many people have dubbed oxytocin as the “hormone of love”, as reported by Medical News Today[9]. You may also hear people refer to Oxytocin as the “hormone of hugs”. This is because this particular hormone often gets released when two people are hugging each other. The primary functions of oxytocin, however, is to assists with the regulation of functions that are needed during childbirth and breastfeeding.

The Pituitary Gland

The Pituitary Gland

Now that we have discussed the primary part of the brain that controls the entire endocrine system and regulates the release and productions of hormones by glands throughout the body, we should also look at the particular glands that are involved in the endocrine system. We should start with the first gland that is affected by the hormones released by the hypothalamus, which is the pituitary gland, of course. The pituitary gland can be found in a particular area of the head, where the sphenoid bone is located. It is sometimes called the hypophysis and is usually no larger than a pea. The pituitary gland is connected to the hypothalamus, and also to numerous blood vessels that helps to carry hormones products here to different parts of the body, including other glands and, of course, organs.

According to InnerBody, the pituitary gland should be divided into two fundamental sections:

  • Posterior Pituitary – This part of the pituitary gland consists solely of nervous tissue. The posterior pituitary produces two kinds of hormones, which includes oxytocin and antidiuretic hormone. Oxytocin assists with the regulation of contractions when childbirth is underway, and assists with releasing milk from the breasts when the newborn child is breastfeeding. Antidiuretic hormones help to avoid the body from losing too much water.
  • Anterior Pituitary – Medical experts often consider the anterior pituitary as the “real pituitary gland”. This particular gland, or at least part of the pituitary gland, is regulated by the hypothalamus. When the hypothalamus releases hormones and sends them to the anterior pituitary gland, it reacts by releasing particular forms of hormones into the body.

While the posterior pituitary is only responsible for secreting two hormones, the anterior pituitary releases quite a large number of hormones that interacts with other glands, as well as certain parts of the human body. Let’s take a quick look at the particular hormones products and released by the anterior pituitary.

  • Thyroid Stimulating Hormone – This hormone is produced by the anterior pituitary and then travels toward the thyroid gland, which it stimulates to cause the release of other hormones.
  • Adrenocorticotropic Hormone – This hormone is also produced by the anterior pituitary and then travels toward the adrenal gland. Instead of stimulating the entire adrenal gland, however, adrenocorticotropic hormones rather only stimulates the adrenal cortex.
  • Follicle Stimulating Hormone – The stimulating follicle hormone has an important part to play in the reproductive system. It is also produced in the anterior pituitary and then travels to the reproductive organs. In both men and women, this hormone stimulates follicle cells on the particular patient’s reproductive organs. In turn, the reproductive organs produces appropriate substances, such as sperm in the male reproductive system.
  • Luteinizing Hormone – Luteinizing hormones are responsible for the stimulation of the reproductive system to activate the production of sex hormones in the patient. The particular sex hormones that this substance causes to be excreted depends on the particular patient’s gender. In men, testosterone will be produced, whereas, in women, estrogen will rather be produced.
  • Human Growth Hormone – Human Growth hormone has an important impact throughout the entire body and is especially essential during earlier growth. This hormone can affect any cell in the body in three primary ways: by stimulating the cell’s growth rate, reproduction rate or by repairing the damage that has been done to the particular cell.
  • Prolactin – Prolactin has a large number of functions in the body, but it is mostly known for its ability to stimulate a woman’s mammary glands; thus resulting in the production of milk, which is excreted through the nipples during breastfeeding sessions.

The Pineal Gland

Pineal Gland

The pineal gland’s function is not as well-known as the pituitary gland and some of the other glands in the human body, but still has an important role to play in the body. This particular gland is shaped somewhat like a pinecone. It is also situated in the brain, in the thalamus region to be more precise. The pineal gland’s sole purpose is to produce a hormone known as melatonin. This particular hormone assists with the sleep-wake cycle of a patient. This particular “cycle” is often also called the circadian rhythm. When more melatonin is produced in the brain, then a patient is likely to experience drowsiness as a symptom, which may indicate to them that nighttime has fallen.

The Thyroid Gland

The thyroid gland[10] is a relatively well-known part of the endocrine system. Some may have heard the name before, but are not entirely sure how this particular gland work, what hormones it excretes and what purposes it serves. Firstly, the thyroid gland is shaped like a butterfly. It can be found at the neck’s base. It is also wrapped around the trachea at both lateral sides. Unlike the pituitary gland, which produces a large variety of hormones, the thyroid gland is only responsible for the production of three essential hormones. The thyroid gland is primarily responsible for aiding in the metabolic functioning of the body, as well as reducing certain mineral levels when they become too high.

The three particular hormones that are produced and released by the thyroid gland include:

  • T3 & T4 – Also known as triiodothyronine and thyroxine, respectively, these two hormones work in combination with each other to assist with the regulation of metabolism. When the production of these two particular hormones is increased, the cellular activity in the body increases significantly, depending on how much of these hormones are being produced. In addition, the usage of energy throughout the patient’s body is also enhanced based on the level of these hormones present in their bodies and produced by the thyroid gland.
  • Calcitonin – Calcium and iron are both essential minerals that the body needs actively to function normally, but high levels of these minerals can be a negative trait for the wellbeing of the human body. Calcitonin’s[11] function is to assist with the absorption of calcium. In addition, the hormone also helps enhance the process where calcium is added to bones to make bones stronger and healthier, as well as less brittle.

Parathyroid Glands

Parathyroid Glands

At the rear side of the thyroid gland, you will find the parathyroid glands[12]. These four glandular tissue masses produces parathyroid hormones, often simply referred to as PTH. These hormones are released when calcium levels in the blood circulatory system becomes too low. When the parathyroid glands produces parathyroid hormones, it causes free calcium ions to be released into the blood circulatory system to help increase the calcium level in the patient’s body. The parathyroid hormones can also act upon the kidneys, causing these organs to preserve left-over calcium ions by depositing them back into the blood circulatory system during their filtration process.

Adrenal Glands

The adrenal glands are also part of the endocrine system and can be found near the kidneys. These glands have a somewhat triangular appearance and each of them are made up of two layers, each providing its own particularly important function in the endocrine system of the human body. Let’s consider each of the two layers separately and also take a look at the hormones produced by these layers, as well as the functions that the layers and hormones play in the human body.

Adrenal Cortex

The outer layer of the adrenal glands is called the adrenal cortex. This particular layer produces three different classes of cortical hormones, each having their own unique role to play.

  • Androgens – A small amount of androgens are produced in the adrenal cortex. Androgens are then used to control the activity of the body’s cells that responds to male hormones, such as testosterone. In addition to its ability to control the activity of these cells, androgen is also able to regulate the growth of male hormone receptive cells throughout the body.
  • Glucocorticoids – It is quite difficult to describe glucocorticoids since there are different types of these hormones. They are primarily responsible for the breakdown of certain substances and then for the conversion of these broken down substances to glucose. Glucocorticoids breaks down both lipids and proteins. It is also vital to understand that these hormones play a role in the maintenance of the immune system and the body’s inflammatory response as well. When the hormones are produced in a healthy manner, they will exhibit anti-inflammatory properties.
  • Mineralocorticoids – Another important class of hormones produced by the adrenal cortex, mineralocorticoids helps to keep the balance of minerals found in the human body at a good balance.

Pancreas

Pancreas

The pancreas is often considered a type of organ in the body but, in reality, this particular body part is also another gland that forms part of the endocrine system within the human body. The pancreas can be found situated close to the stomach. This gland is classified as a heterocrine gland. It consists of approximately 1% endocrine tissue, amongst others, as well as exocrine tissue. The cells contained within the small concentration of endocrine tissue can be split into two groups, each with a unique function in the human body:

  • Alpha Cells – Alpha cells are responsible for producing a hormone known as glucagon. Glucagon hormones, in turn, then causes an increase in blood sugar levels. Raising blood sugar levels isn’t the only function of glucagon; thus we should look at how this particular hormone works. When glucagon hormones go to work, they break polysaccharide glycogen from liver cells and muscle cells, which then causes glucose to be released into the blood circulatory system. This is when blood sugar levels start to increase.
  • Beta Cells – Beta cells have quite the opposite function as compared to alpha cells in the pancreas. While alpha cells are responsible for increasing blood glucose levels, beta cells rather help to reduce the level of blood glucose in the patient’s blood circulatory system. Beta cells achieves this goal by excreting insulin hormones, which then absorbs the glucose found in blood cells after a meal was consumed.

Adrenal Medulla

At the center of the adrenal glands lies the adrenal medulla. When the autonomic nervous system goes through a process called sympathetic division, the adrenal medulla is stimulated by the nervous system, which, in turn, causes this particular part of the adrenal glands to release two particular forms of hormones. The hormones produced and released by the adrenal medulla include:

  • Epinephrine – Have you ever heard someone speak of an “adrenaline rush”? Well, then you’re about to find out what exactly the most important word in that term means – adrenaline. Yes, the other name for epinephrine[13], which is also much more commonly used, is adrenaline. This particular type of hormone is a tyrosine-derived hormone. Tyrosine is classified as an amino acid. The particular function of epinephrine is to assist with the response by the human body that is often referred to as its “flight or fight” ability. In short, adrenaline allows us to react to a potentially dangerous conditions that may pose as a threat to us.
  • Norepinephrine – Norepinephrine[14] is often also called noradrenaline. This hormone works with epinephrine, or adrenaline, to offer a more effective “fight or flight” mechanism to the human body. Norepinephrine is classified as a catecholamine. It acts as both a hormone and a neurotransmitter.

Reproductive System

Reproductive Systems

In addition to the glands that we discussed, it is also essentially important to take a look at the reproductive system as well. Here, you can find glands that are unique to each particular gender – they are referred to as the gonads. The gonads of a man would include his testes, but in a woman, her gonads would include her ovaries. These two glands produce two different primary hormones, each with a unique function for the particular gender in question.

  • Testosterone – Testosterone is a hormone that people often associate with men that have large muscles, but this isn’t always the case. Testosterone is a type of androgen hormone and its production starts at puberty. This is when hair starts to grow in weird places, such as the genital region, the underarms and the chest. Later in life, when a man reaches adulthood, testosterone maintains his sex drive, muscle mass, bone density and even contributes to a healthy heart.
  • Estrogen – While testosterone is the primary hormone in the male body, estrogen is a more prevalent type of sex hormone in the female body. The ovaries of a woman, which is a unique part of her reproductive system, is responsible for producing these hormones. In addition to estrogen, a woman’s ovaries will also produce some progesterone. Progesterone is found in higher volumes when a woman is ovulating and while she is pregnant.

Also See: Oxytocin: The Hormone behind Our Love

Conclusion

While often overlooked when symptoms develop in a patient, the endocrine system plays an essential part in keeping the body’s organs and other systems regulated, and in balance. When glands produce too much hormones or its ability to produce an adequate supply of particular hormones are compromised in some way, then various symptoms and issues may develop in a patient. This can lead to the development of diseases, as well as certain physical and mental issues that may be unpleasant to the patient. In some cases, the disease may also affect the endocrine system and inhibit its optimum functionality, causing similar problems to develop. Being educated about the signs that are associated with problems that may occur in the endocrine system may help a patient detects a developing condition at an early stage, which can lead to a more successful treatment plan that gets rid of the underlying causes before the glands throughout the body, as well as hormone levels, are affected at a significant level.

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Feature Image: Istockphoto.com
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Author

Contributor : Dr. Ahmed Zayed ()

This Article Has Been Published on July 13, 2017 and Last Modified on December 10, 2018

Dr. Ahmed Zayed Helmy holds a baccalaureate of Medicine and Surgery. He has completed his degree in 2011 at the University of Alexandria, Egypt. Dr. Ahmed believes in providing knowledgeable information to readers. Other than his passion for writing, currently he is working as a Plastic surgeon and is doing his masters at Ain Shams University. You can connect with him on Linkedin.

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