The Endocrine System and Glands of the Human Body: Function and Disorders

Written by Barbara Brody

• What Is the Endocrine System?
• What Is a Gland?
• Endocrine System Functions
• Parts of the Endocrine System
• Health Issues
• Endocrine System Disorders
• More

The endocrine system is a network of glands in your body that make the hormones that help cells talk to each other. They’re responsible for almost every cell, organ, and function in your body.

If your endocrine system isn’t healthy, you might have problems developing during puberty, getting pregnant, or managing stress. You also might gain weight easily, have weak bones, or lack energy because too much sugar stays in your blood instead of moving into your cells where it’s needed for energy.

A gland is an organ that makes and puts out hormones that do a specific job in your body. Endocrine and exocrine glands release the substances they make into your bloodstream.

Your endocrine system:

• Makes hormones that control your moods, growth and development, metabolism, organs, and reproduction
• Controls how your hormones are released
• Sends those hormones into your bloodstream so they can travel to other body parts

Many glands make up the endocrine system. The hypothalamus, pituitary gland, and pineal gland are in your brain. The thyroid and parathyroid glands are in your neck. The thymus is between your lungs, the adrenals are on top of your kidneys, and the pancreas is behind your stomach. Your ovaries (if you’re a woman) or testes (if you’re a man) are in your pelvic region.

• Hypothalamus. This organ connects your endocrine system with your nervous system. Its main job is to tell your pituitary gland to start or stop making hormones.
• Pituitary gland. This is your endocrine system’s master gland. It uses information it gets from your brain to tell other glands in your body what to do. It makes many important hormones, including growth hormone; prolactin, which helps breastfeeding moms make milk; antidiuretic hormone(ADH) (vasopressin), which controls blood pressure and helps control body water balance through its effect on the kidney, corticotropin /ACTH: Adrenocorticotrophic hormone. which stimulates the adrenal gland to make certain hormones, thyroid-stimulating hormone (TSH), which stimulates the production and secretion of thyroid hormones, oxytocin which helps in milk ejection during breast feeding; and luteinizing hormone, which manages estrogen in women and testosterone in men.
• Pineal gland. It makes a chemical called melatonin that helps your body get ready to go to sleep.
• Thyroid gland. This gland makes thyroid hormone, which controls your growth and metabolism. If this gland doesn’t make enough (a condition called hypothyroidism), everything happens more slowly. Your heart rate might slow down. You could get constipated. And you might gain weight. If it makes too much (hyperthyroidism), everything speeds up. Your heart might race. You could have diarrhea. And you might lose weight without trying. The thyroid gland also produces the hormone calcitonin, which may contribute to bone strength by helping calcium to be incorporated into bone.
• Parathyroid. This is a set of four small glands behind your thyroid. They play a role in bone health. The glands control your levels of calcium and phosphorus.
• Thymus. This gland makes white blood cells called T-lymphocytes that fight infection and are crucial as a child’s immune system develops. The thymus starts to shrink after puberty.
• Adrenals. Best known for making the “fight or flight” hormone adrenaline (also called epinephrine), these two glands also make hormones called corticosteroids. They affect your metabolism heart rate, oxygen intake, blood flow, and sexual function, among other things.
• Pancreas. This organ is part of both your digestive and endocrine systems. It makes digestive enzymes that break down food. It also makes the hormones insulin and glucagon. These ensure you have the right amount of sugar in your bloodstream and your cells.
• If you don’t make insulin, which is the case for people with type 1 diabetes, your blood sugar levels can get dangerously high. In type 2 diabetes, the pancreas usually makes some insulin but not enough.
• Ovaries. In women, these organs make estrogen and progesterone. These hormones help develop breasts at puberty, regulate the menstrual cycle, and support a pregnancy.
• Testes. In men, the testes make testosterone. It helps them grow facial and body hair at puberty. It also tells the penis to grow larger and plays a role in making sperm.

As you get older, it’s natural to notice some things related to your endocrine system. Your metabolism tends to slow down. So you might gain weight even though you haven’t changed how you eat or exercise. Hormonal shifts also explain, at least in part, why you’re more likely to have heart disease, osteoporosis, and type 2 diabetes as you age.

No matter how old you are, stress, infections, and being around certain chemicals can also mess with parts of your endocrine system. And genetics or lifestyle habits can increase your chances of an endocrine disorder like hypothyroidism, diabetes, or osteoporosis.

• Acromegaly. Sometimes the pituitary gland makes too much growth hormone and your bones get bigger. It usually affects your hands, feet, and face. It usually starts in middle age.
• Adrenal insufficiency. When you have this, your adrenal glands don’t make enough of certain hormones, like cortisol, which controls stress.
• Cushing’s disease. In this, your body makes too much cortisol. You could gain weight, get stretch marks, bruise easily at first, then get weakened muscles and bones and possibly develop a hump on your upper back.
• Hyperthyroidism. This is when your thyroid gland makes more hormones than your body needs. You might hear it called overactive thyroid. It makes your system run fast and you might feel nervous, lose weight, and have a rapid heartbeat or trouble sleeping.
• Hypothyroidism. When your body doesn’t make enough thyroid hormone, your system slows down. You might feel tired, gain weight, have a slow heartbeat, and get joint and muscle pains.
• Hypopituitarism. Sometimes your pituitary gland doesn’t make enough of certain hormones and your adrenal and thyroid glands can’t work right.
• Multiple endocrine neoplasia. This is a group of disorders that affect your endocrine system. It causes tumors on at least two endocrine glands or in other organs and tissues.
• Polycystic ovary syndrome. An imbalance of reproductive hormones can cause your ovaries to either not make an egg or not release it during ovulation. This can throw off your periods, cause acne, and make hair to grow on your face or chin.
• Precocious puberty. When glands that control reproduction don’t work properly, some kids start puberty abnormally early — around 8 in girls and 9 in boys.

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What Is It, Functions, Organs & Conditions

The endocrine system is a network of glands and organs located throughout the body. It’s similar to the nervous system in that it plays a vital role in controlling and regulating many of the body’s functions.

However, while the nervous system uses nerve impulses and neurotransmitters for communication, the endocrine system uses chemical messengers called hormones.

Keep reading to discover more about the endocrine system, what it does, and the hormones it produces.

The endocrine system is responsible for regulating a range of bodily functions through the release of hormones.

Hormones are secreted by the glands of the endocrine system, traveling through the bloodstream to various organs and tissues in the body. The hormones then tell these organs and tissues what to do or how to function.

Some examples of bodily functions that are controlled by the endocrine system include:

• metabolism
• growth and development
• sexual function and reproduction
• heart rate
• blood pressure
• appetite
• sleeping and waking cycles
• body temperature

What is a gland?

A gland is an organ that creates and releases substances that the body needs to function. There are two types of glands:

• endocrine glands, which release hormones directly into the bloodstream
• exocrine glands, like lymph nodes and sweat glands, which are not part of the endocrine system

The glands of the endocrine system are where hormones are produced, stored, and released. Each gland produces one or more hormones, which go on to target specific organs and tissues in the body.

The glands of the endocrine system include the:

• Hypothalamus. While some people don’t consider it a gland, the hypothalamus produces multiple hormones that control the pituitary gland. It’s also involved in regulating many functions, including sleep-wake cycles, body temperature, and appetite. It can also regulate the function of other endocrine glands.
• Pituitary. The pituitary gland is located below the hypothalamus. The hormones it produces affect growth and reproduction. They can also control the function of other endocrine glands.
• Pineal. This gland is found in the middle of your brain. It’s important for your sleep-wake cycles.
• Thyroid. The thyroid gland is located in the front part of your neck. It’s very important for metabolism.
• Parathyroid. Also located in the front of your neck, the parathyroid gland is important for maintaining control of calcium levels in your bones and blood.
• Thymus. Located in the upper torso, the thymus is active until puberty and produces hormones that are important for the development of a type of white blood cell called a T cell.
• Adrenal. One adrenal gland can be found on top of each kidney. These glands produce hormones that are important for regulating functions such as blood pressure, heart rate, and stress response.
• Pancreas. The pancreas is located in your abdomen behind your stomach. Its endocrine function involves controlling blood sugar levels.

Some endocrine glands also have non-endocrine functions. For example, the ovaries and testes produce hormones, but they also have the non-endocrine function of producing eggs and sperm, respectively.

Hormones are the chemicals the endocrine system uses to send messages to organs and tissue throughout the body. Once released into the bloodstream, hormones travel to their target organ or tissue, which has receptors that recognize and react to the hormone.

Below are some examples of hormones that are produced by the endocrine system.

Explore the interactive 3-D diagram below to learn more about the endocrine system.

Sometimes, hormone levels can be too high or too low. When this happens, it can have a number of effects on your health. The signs and symptoms depend on the hormone that’s out of balance.

Here’s a look at some conditions that can affect the endocrine system and alter your hormone levels.

Hyperthyroidism

Hyperthyroidism happens when your thyroid gland makes more thyroid hormone than necessary. This can be caused by a range of things, including autoimmune conditions.

Some common symptoms of hyperthyroidism include:

• fatigue
• nervousness
• weight loss
• diarrhea
• issues tolerating heat
• fast heart rate
• trouble sleeping

Treatment depends on how severe the condition is, as well as its underlying cause. Options include medications, radioiodine therapy, or surgery.

Graves‘ disease is an autoimmune disorder and a common form of hyperthyroidism. In people with Graves‘ disease, the immune system attacks the thyroid, which causes it to produce more thyroid hormone than usual.

Hypothyroidism

Hypothyroidism occurs when your thyroid doesn’t produce enough thyroid hormone. Similar to hyperthyroidism, it has many potential causes.

Some common symptoms of hypothyroidism include:

• fatigue
• weight gain
• constipation
• issues tolerating the cold
• dry skin and hair
• slow heart rate
• irregular periods
• fertility issues

Treatment for hypothyroidism involves supplementing your thyroid hormone with medication.

Cushing syndrome

Cushing syndrome happens due to high levels of the hormone cortisol.

Common symptoms of Cushing syndrome include:

• weight gain
• fatty deposits in the face, midsection, or shoulders
• stretch marks, particularly on the arms, thighs, and abdomen
• slow healing of cuts, scrapes, and insect bites
• thin skin that bruises easily
• irregular periods
• decreased sex drive and fertility in males

Treatment depends on the cause of the condition and can include medications, radiation therapy, or surgery.

Addison’s disease

Addison’s disease happens when your adrenal glands don’t produce enough cortisol or aldosterone. Some symptoms of Addison’s disease include:

• fatigue
• weight loss
• abdominal pain
• low blood sugar
• nausea or vomiting
• diarrhea
• irritability
• a craving for salt or salty foods
• irregular periods

Treatment for Addison’s disease involves taking medications that help replace the hormones your body isn’t producing enough of.

Diabetes

Diabetes refers to a condition in which your blood sugar levels aren’t regulated within a certain range.

People with diabetes have too much glucose in their blood (high blood sugar). There are two types of diabetes: type 1 diabetes and type 2 diabetes.

Some common symptoms of diabetes include:

• fatigue
• increased hunger or thirst
• frequent urge to urinate
• irritability
• frequent infections

Treatment for diabetes can include blood sugar monitoring, insulin therapy, and medications. Lifestyle changes, such as getting regular exercise and eating a balanced diet, can also help.

Polycystic ovary syndrome (PCOS)

This common condition is caused by unbalanced reproductive hormones in people with ovaries, which can create issues in the ovaries. Living with PCOS can mean that an egg may not be released every month, or may not develop as it should when it is released.

Some of the common symptoms of PCOS are:

• irregular periods
• fertility issues
• cysts that form on the ovaries
• acne
• hirsutism, which is an unusual amount of hair growth on the face or chin
• thinning hair
• weight gain
• skin tags

Treatment for PCOS focuses on easing the symptoms. Treatments include medications, like birth control and metformin, and lifestyle changes, such as focusing on nutrition and trying to reach a moderate weight if your doctor has recommended it.

Hypogonadism

A common condition, especially in older males and occasionally in females, hypogonadism is caused by a lowered production of the sex hormone testosterone. This can lead to lowered libido, as well as a variety of other symptoms, such as:

• erectile dysfunction in people with a penis
• reduced energy
• reduced muscle mass
• depressed mood
• increased irritability

Treatment for hypogonadism focuses on improved testosterone levels. Testosterone replacement therapy and lifestyle changes (such as working toward a moderate weight if your doctor has recommended it) are two popular methods.

Osteoporosis

Osteoporosis is an abnormal loss of bone mass and changes in bone tissue. It can be caused by a variety of issues, but two common causes are lowered estrogen levels in people with ovaries and lowered testosterone levels in people with testicles. These lowered hormone levels can be caused by age, as well as other diseases.

Osteoporosis doesn‘t always cause obvious symptoms. But some of the more common symptoms are bone fractures and injuries related to minor falls, lifting, and even coughing.

Treatment for osteoporosis focuses on slowing or stopping bone loss. Proper nutrition, exercise, and medications are three of the most common treatments.

Acromegaly

This rare disease is caused when the body makes too much growth hormone, which is mainly produced in the pituitary gland. Mostly diagnosed in middle-aged adults, it can cause organs, bones, cartilage, organs, and certain tissues to grow in size.

The common symptoms of acromegaly include:

• swollen nose
• swollen ears
• swollen hands and feet
• joint aches
• a deeper voice than usual
• an increase in sweating and body odor

Treatment for acromegaly includes medications, radiation therapy, and surgery.

The endocrine system is a complex collection of glands and organs that helps regulate various bodily functions. This is accomplished through the release of hormones, or chemical messengers, produced by the endocrine system.

Human endocrine system

The definition and description of the composition of the human endocrine system, consisting of endocrine glands: hypothalamus, pituitary, pineal, thyroid, thymus, pancreas, adrenal glands, gonads. A description of the types of hormones and the features of their functioning in the human body, as well as factors affecting the result of the action of the hormone is given.

Definition

Endocrine system – a set of structures: organs, parts of organs, individual cells that secrete highly active regulatory factors – hormones into the blood, lymph and intercellular fluid.

The relationship between the nervous and endocrine systems

Biochemical and physiological processes in various organs and tissues proceed in a strictly orderly and coordinated manner due to the presence of regulatory systems that coordinate these processes. Regulatory systems play a particularly important role in maintaining metabolic homeostasis during muscle activity, when the intensity of the use of substances increases and their metabolism changes.

Metabolism (metabolism) is a complex of biochemical and physiological processes that ensures the intake of substances from the environment into the body, their assimilation, transformation in tissues, and the removal of metabolic products (metabolites) from the body into the external environment.

You can read about the relationship between hormones and muscle mass in my book:

Hormones and human skeletal muscle hypertrophy

The main regulatory systems of the human body are the nervous and endocrine systems. There is a close relationship and subordination between the nervous and endocrine systems. The nervous system through the endocrine system controls the metabolism, and the endocrine system affects this control. The hypothalamus is the coordinating center of these systems.

Composition of the endocrine system

The endocrine system consists of specialized endocrine glands , or endocrine glands. The main endocrine glands are: hypothalamus, pituitary gland, pineal gland, thyroid gland, thymus, pancreas, adrenal glands, gonads (testicles, ovaries) (Fig. 1).

Fig.1. Human endocrine glands

Types of hormones

Endocrine glands secrete biologically active substances – hormones – into the blood. According to the chemical structure, hormones are divided into three types: steroid, protein-peptide and amino acid derivatives.

Functioning of hormones in the human body

Hormones enter the blood in small amounts and, after being transported by the blood, have a regulating effect on the metabolism and physiological functions of target organs. In the cells of target organs, there are special proteins called hormone receptors. These proteins are either inside the cells of the target organ (if the chemical nature of the hormone is a steroid) or embedded in the outer membrane of the cells of the target organ (if the chemical nature of the hormone is a protein or amino acid derivatives). Hormone receptors are able to bind only to certain hormones, so target organs selectively extract from the flowing blood only those hormones that are necessary for this organ to regulate its metabolism.

Factors affecting the result of the action of the hormone

The result of the action of the hormone is affected by: the concentration of the hormone in the blood; free or associated with the transport protein state of the hormone; state of the target tissue; the number of active receptors.

Literature

1. Samsonova, AV Hormones and human skeletal muscle hypertrophy: Proc. allowance. – St. Petersburg: Kinetics, 2019. – 204 p.: ill.

Best regards, A.V. Samsonova

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Endocrine system. Humoral regulation – what is it, definition and answer

All glands of the body are usually divided into glands:

• Internal secretion = endocrine (they secrete hormone into the blood): thyroid gland, pituitary gland, adrenal glands, pineal gland, thymus.

• External (excrete into the body cavity or beyond): sweat, sebaceous, salivary, mammary glands.

• Mixed secretion (hormone + secretion into the blood + into the body cavity or beyond): pancreas, gonads.

All endocrine glands secrete hormones.

Hormones are biologically active substances that are produced in specialized cells of the endocrine glands, enter the blood and have a regulatory effect on metabolism and physiological functions.

Pituitary gland (interbrain)

Pituitary gland is the most important gland that regulates many functions of the body, some of its hormones control the activity of other endocrine glands, for example, pituitary hormone thyrotropin stimulates the production and activation of thyroxine, a thyroid hormone.

Other hormones also have a tremendous effect on the body, for example, somatotropin (growth hormone) regulates the growth of the body at a young age, with a lack of it, dwarfism will develop, and with an excess, gigantism.

Epiphysis (midbrain)

This endocrine gland plays the role of a “biological clock”. Receiving information about the time of day from the visual analyzer, the pineal gland controls the production of melatonin . This hormone is responsible for the regulation of circadian rhythms, that is, for the desire to sleep and stay awake.

Pineal hormones also affect the functions of the pituitary gland (hormone serotonin ), thyroid gland, adrenal glands, control puberty and inhibit the function of the gonads in childhood.

Thymus

In the chest behind the sternum there is thymus, or thymus gland. It consists of two lobes resembling the horns of a fork. Its value changes with age – in childhood, the thymus is much larger than in adulthood.

Thymus is the central organ of the immune system.

Immune cells are formed and trained in it, harmful agents are “remembered”, the formation of immunity depends on it.

Thyroid and parathyroid glands

Thyroid gland is the largest endocrine gland of internal secretion. It consists of two lobes that hug the upper part of the trachea like a tie. On the back surface are 4 parathyroid (parathyroid) glands.

Thyroxine – the most important thyroid hormone, it affects the entire body and regulates metabolism. Iodine is required for its synthesis.

With hypofunction (deficiency) of thyroxin, adults develop myxedema , which is expressed in swelling, decreased metabolism and excitability of the nervous system, and obesity. Children will develop dwarfism with a violation of body proportions and cretinism.

With hyperfunction (excess) of thyroxin, increased excitability of the nervous system, increased metabolism, weight loss, the appearance of goiter – an increase in the thyroid gland in size.

Another thyroid hormone calcitonin is responsible for controlling the amount of calcium in the blood. Together with parathyroid hormones, it maintains the level of calcium in the blood within the normal range.

Adrenals

Adrenal glands – paired glands that are located at the tops of the kidneys. They consist of inner (brain) and outer (cortical) layers.

The hormone of the inner layer adrenaline accelerates the work of the heart, constricts blood vessels, slows down digestion, increases the amount of glucose in the blood.

Outer layer hormones corticoids regulate the metabolism of mineral and organic substances, the release of sex hormones, the activity of allergic and inflammatory reactions.

Pancreas

Pancreas – large gland mixed secretion. It secretes digestive enzymes into the duodenal cavity, and the hormone insulin into the blood (endocrine function).

Insulin regulates blood glucose, glycogen synthesis from excess glucose, fat deposition.

Hypofunction develops a disease such as diabetes mellitus, which is accompanied by an increase in blood sugar, the appearance of sugar in the urine, increased pressure and blood viscosity, and many other side effects.

In case of hyperfunction of the pancreas, there is a lack of glucose in the blood, the brain may lack nutrition and the person may fall into a coma.

Sex glands

Sex glands, or gonads – testes (testicles) in men and ovaries in women are among the glands with mixed secretion.

Gonads are referred to glands of mixed secretion .

Sex hormones promote embryonic differentiation, in the subsequent development of the genital organs and the appearance of secondary sexual characteristics, determine puberty and human behavior.

Male sex hormones (androgens)

All sex hormones are synthesized from a single precursor, cholesterol. The most important of the androgens is testosterone.

Female sex hormones

These hormones are produced in the female sex glands – the ovaries, during pregnancy – in the placenta. Men also produce female sex hormones, just in smaller quantities. It occurs in the cells of the testicles.

Ovarian follicles synthesize estrogens ( stimulate the development of primary and secondary female sexual characteristics, the development and growth of the mammary glands, affect the development of the bone skeleton, the emotional and mental state of women; during pregnancy, estrogens promote the growth of uterine muscle tissue, effective uterine – placental circulation, together with progesterone and prolactin – the development of the mammary glands).

The corpus luteum of the ovary produces progesterone (prepares the uterus for the attachment of a fertilized egg and ensures the normal course of pregnancy; participates in the regulation of the menstrual cycle).

Neurohumoral regulation of the body

Endocrine gland hormones affect the state of the cells of the nervous system. At the same time, the activity of the glands is controlled by the nervous system.