What function can hormones of the endocrine glands perform? The work of the endocrine glands - what they produce, where and how they are secreted. Endocrine glands and their hormones

And their hormones play an important role in the life of every person. Glands are the vital human organs that produce active substances—hormones.

Where do hormones go? After reproduction, they enter the blood stream or cellular fluid in the body. The glands are called intrasecretory because they lack excretory channels and secrete hormonal substances directly to the blood cells.

What organs are included in the internal secretion group? The intrasecretory glands include:

pituitary;
thyroid gland;
parathyroid gland;

sexual;
adrenal glands

The stability of the endocrine glands affects human health. The general well-being of the patient depends on the functionality of any of them. The more evenly hormones are released, the more smoothly the body works.

There are also other types of glands in the body. They carry out the process of releasing hormones into the blood and intestinal cavity and at the same time carrying out endocrine and exocrine functions. Hormones produced by endocrine glands are carried in the blood throughout the human body, activating only in a specific organ, the functioning of which they regulate.

Organs capable of carrying out exocrine and intrasecretory processes:

the pancreas produces hormones and gastric juice involved in the digestive process;
the gonads produce hormonal particles and reproductive materials;
thymus.

The placenta and thymus gland also have a combination of hormone production and non-endocrine processes. The mixed type of glands is also often referred to by doctors as glands of the intrasecretory type, since together they form a single endocrine system. It is still unknown whether medicine will distinguish this type as a separate one in the future.

Thanks to the particles that are produced by the endocrine glands, with the assistance of the fluid environment of the body, physiological processes are regulated. Hormones secreted by the endocrine glands are active agents of the pituitary gland.

Due to the fact that all glands are innervated by the nervous system, the production of hormones depends on nervous regulation. Thus, a single neurohumoral regulation network is created by humoral and nervous regulation.

The main feature of hormonal substances is that they affect certain metabolic processes or cell groups. This organic substance has a different chemical composition and, even when produced in small quantities, has very high biological activity.

With their help, the level of intensity of the metabolic process can change, they affect the development and renewal of cells. Development during puberty also depends on hormones.

The effect of hormones on tissues is different. Some can bind to receptor proteins, while others can enter the cell and activate a specific gene. During the process of DNA synthesis and subsequent enzyme synthesis, the activity and direction of the metabolic function changes.

There is a hormonal connection between the organs: the hormones of one gland affect the work of the other gland, thereby ensuring mutual coordination.

Pituitary gland and its functions

The main coordinator in this is.

The pituitary gland is divided into three parts: anterior, middle and posterior. Each gland produces separate substances. This organ stimulates the production of the following substances:

improving synthesis and secretion processes;
thyrotropins secreted by the thyroid gland;
corticotropins in the adrenal glands;
gonadotropin in the gonads.

The effect of the hormone on the body:

lipotropin – effect on fat metabolism;
somatotropin – human growth and development from childhood;
melanotropin - produced by the middle part of the pituitary gland, affects the pigmentation of human skin.

In the posterior part of the pituitary gland, oxytocin enhances the work of the kidneys and smooth muscle of the uterus. With a lack of oxytocin, a person is more irritable. Thanks to oxytocin, mother's milk is produced.

Prolactin is also produced in the pituitary gland. Together with progesterones, it affects the development of a woman’s mammary glands. This substance is also called stress. When the hormone level increases, mastopathy and discomfort may occur.

Hormones also control not only human growth, but also control the functionality of the thyroid gland and adrenal glands.

Thyroid hormones

This organ is located in the neck in front of the trachea near the thyroid cartilage. It is divided into two parts connected to each other. Substances are produced that help regulate metabolic function and increase the performance of the nervous system: thyroxine and triiodothyronine.

Due to excess hormones, the following disorders occur:

the activity of the metabolic function increases;
goiter develops;
bulging eyes appear;
chronic pathologies.

In case of hormone deficiency, the opposite symptoms appear:

metabolism deteriorates;
lethargy, apathy, and drowsiness appear;

legs swell regularly;
Children's growth stops and physical and mental development is hampered.

Thyroxine

A person’s well-being and mood state depend on this hormone. It is a forming substance in the human body. There is control over the functioning of the gallbladder and kidneys.

Action of parathyroid hormone

Produced by the parathyroid glands, which are located at the back of the thyroid gland. The substance controls the metabolic process of calcium and phosphorus. With high activity of the gland, calcium from bone tissue enters the blood in an increased volume.

Calcium and phosphorus are excreted from the body through the kidneys. The consequence of this process is the formation of kidney stones and weakening of muscle tissue.

The result of such disorders is paralysis of the respiratory muscles with a fatal outcome for the patient. Such pathologies must be treated immediately after the first symptoms appear; they should not be neglected at any age.

Production of thymosin, thymopoietin and thymalin

These substances are produced by the thymus gland, located behind the chest. The gland promotes the production of lymphocytes and the immunological defense response. In children, with the help of the gland, immunity is formed and its activity is higher than in an adult.

Pancreatic hormones

These are insulin, glucagon and somatostanin. Located under the stomach and secretes gastric juice.

Glucagon promotes the breakdown of glycogen and increases glucose levels in tissues. An excess of glucagon leads to the breakdown of fats, and a deficiency leads to a decrease in glucose levels.

The action of insulin reduces the amount of glucose in cells. Glucose is processed and energy is released, glycogen is synthesized and fat is deposited.

Somatostatin reduces glucagon production.

Adrenal glands and secreted substances

Location - above the upper part of the kidneys. They are divided into cortical and medulla layers.

The cortical, or upper layer, produces corticoids, on which the regulation of mineral and organic matter, the production of sex hormones, and the suppression of an allergic or inflammatory reaction depend.

Cortisol and aldosterone are very important. They are distinguished by the cortical layer. With their help, an immune defense reaction, a barrier against stress, and activation of the heart muscle and brain are launched. Therefore, it is necessary to control its production by the glands. regulates the following processes:

water-salt metabolism function;
the volume of potassium in the cells of the body;
the amount of sodium in the body.

The adrenal medulla produces epinephrine and norepinephrine, which regulate:

work of the cardiovascular system;
digestion process;
function of glycogen breakdown.

Equivalence of released substances

Hormones of all types and any gland in the human body are of equal importance. Depending on the excess, deficiency or absence of any substance, the functions of the glands will become more complicated or the functioning of the body systems will be disrupted. In addition to the glands of the endocrine system, these substances can be secreted in other human organs.

To understand where the hormone secreted by the endocrine glands goes, it is necessary to study in detail the work of the glands themselves.

Any gland and the hormones it produces affect the overall health of a person. Hormonal imbalance negatively affects the functioning of all organs and systems. Internal secretion is a complex apparatus in the human body; it must be protected from negative influences. The production of hormones depends not only on external factors affecting the body, but also on each organ and its condition as a whole.

The science of endocrinology studies the endocrine glands, their disorders, as well as the hormones secreted by these glands.

The hypothalamic-pituitary system is a close connection between the endocrine and nervous parts of the human body, which is why it is called the neuroendocrine system.

To understand how the organs of the endocrine system work, you need to know their anatomy and mechanism of synthesis.

How endocrine organs work:

endocrine glands that synthesize hormones;
they are transported in various ways;
they are accepted by the tissues of the corresponding organs.

Without the normal functioning of the endocrine system, the healthy functioning of the organs and systems of the human body is impossible.

Endocrine glands and their hormones

Hormones are substances that are highly active; they are synthesized by endocrine glands.

These substances are divided depending on their chemical structure. See table:

The properties of hormones are presented in the table:

A small amount of hormones in the blood has a clear effect on organs and systems. The points of their influence are located at a distance from the endocrine glands.

Specificity and selectivity lies in their effect on organs and tissues called targets. Hormones interact with them thanks to receptors, protein molecules that can transform a signal into action, causing certain changes in organs.

Located in the brain, it has properties of the endocrine and nervous systems. The hypothalamus synthesizes vasopressin and oxytocin, which are transported to the pituitary gland; they regulate the functioning of the reproductive system and kidneys.

The pituitary gland produces tropic hormones. It is located at the base of the brain, in a place called the sella turcica. Substances produced by the pituitary gland are listed in the table.

Endocrine thyroid organ

The gland synthesizes iodine-containing substances: thyrocalcitonin, thyroxine, triiodothyronine, substances that regulate the metabolism of phosphorus, calcium, and the level of energy consumption necessary for the whole organism.

The parathyroid glands produce parathyroid hormone, which increases the level of calcium and phosphorus in the blood and maintains it at the required level.

Normal functioning of the thyroid gland and its productivity is ensured by a constant supply of the element iodine in quantities of up to 200 mcg. A person receives iodine from food, water and air.

Iodine in the intestines is broken down into iodides and taken up by the thyroid gland. The synthesis of thyroid substances is carried out only with pure elemental iodine, obtained using the enzymes cytochrome oxidase and peroxidase. The entry of iodides into the thyroid gland and their oxidation is carried out by the pituitary thyrotropin.

Lack of iodine is the main cause of thyroid problems and hormonal deficiency, causing disruption in the functioning of all organs, a decline in immunity and a decrease in intellectual activity.

The functioning of the adenohypophysis and thyroid gland is carried out by the hypothalamus, the main regulator of the endocrine system. Thyroliberin produced by this organ stimulates the production of thyrotropin in the pituitary gland.

Adrenal glands

Hormones in the adrenal glands are secreted in the medulla and cortex. Corticosteroids are synthesized in the cortex.

The cortex is divided into three zones in which the hormones indicated in the table are produced.

The medulla supplies catecholamines to the blood: norepinephrine and adrenaline. Norepinephrine regulates nervous processes in the sympathetic zone.

Catecholamines regulate fat and carbohydrate metabolism, help the body adapt to stress, releasing adrenaline in response to emotional stimuli (pain, joy, excitement, horror, anger). Adrenaline is not called the hormone of emotions for nothing.

The endocrine part of the gland, called the islets of Langerhans, produces glucagon, insulin, and somatostatin.

Insulin regulates fat, protein and carbohydrate metabolism.
Glucagon is a stimulator of glucose secretion of insulin.
Somatostatin suppresses the synthesis of growth hormone, insulin and glucagon.

Impaired production of glucagon and insulin leads to diabetes.

Sex glands

Not only hormones are synthesized, but also female eggs and male sperm. Sperm are produced in the male testes. Androgens promote their production. Women's ovaries produce estrogens. Their specialization is female sexual characteristics and their development. The ovaries also produce progesterone, which is necessary for bearing offspring. Control over the synthesis of germ cells is carried out by the adenohypophysis.

Kidneys, heart and central nervous system as endocrine glands

In addition to the excretory function, the kidneys also perform an endocrine function. The juxtaglomerular apparatus synthesizes renin, which regulates vascular tone. The kidneys also synthesize erythropoietin, which is responsible for bone marrow red blood cells.

The heart is also part of the endocrine system; natriuretic hormone, produced in the atrium, influences the kidney's production of sodium.

Enkephalins and endorphins are hormones of the endocrine and nervous systems, synthesized in the central nervous system, their task is pain relief, which is why they are also called “Endrogenic opiates”. Neurohormones act like morphine.

the pituitary gland synthesizes/secretes somatotropic hormone (GH), prolactin, ACTH, etc.;
The adrenal gland contains four layers of cells, each of which synthesizes its own hormone.

The pancreas, from the point of view of a gastroenterologist, is an exocrine organ, since it secretes pancreatic enzymes; from the point of view of an endocrinologist, it is an endocrine organ, since it produces a package of interdependent hormones (insulin, glucagon, somatostatin, etc.).

In addition, some hormones are produced in several places:

catecholamines - not only in the adrenal medulla, but also in the paravertebral nerve ganglia;
somatostatin - both in the islets of Langerhans and in the hypothalamus.

Outside the endocrine glands, microscopic clusters of cells have been found that specialize in the synthesis of biologically active substances with hormone properties:

regulators of hormone secretion from endocrine glands:

the nuclei of the hypothalamus synthesize substances that regulate the secretion of pituitary hormones (somatoliberin, ACTH-releasing hormone, etc.);
accumulations of cells in the intestinal wall that produce incretin hormones;

regulators of organ functions:

hypothalamic nuclei.

Relatively recently, the biologically active substances leptin and adiponectin, synthesized by adipose tissue (adipocytes), were discovered, which were classified as hormones, since they have a systemic regulatory effect - they regulate appetite and energy metabolism.

So, hormones are produced not only by the endocrine gland, as a result of which this quality cannot unambiguously define the concept of “hormone”. At the same time, in modern clinical endocrinology, almost all diseases represent one or another dysfunction of the endocrine gland. In this regard, the definition of a hormone and the associated definition of an endocrine gland in clinical endocrinology still remains “classical”.

Thus, we can give the following, quite complete from a clinical point of view, definition of the hormone.

Hormone- a biologically active substance produced by the endocrine gland, which has a regulating effect on certain structures of the body and metabolism (utilization of substrates from the blood, energy exchange, etc.), which is often manifested by externally visible changes in the body (for example, growth) and/or changes in behavior ( for example, sexual).

In this classic definition, the terms endocrine gland and hormone are interdependent. Hence, the logic of a diagnostic search in clinical endocrinology is obvious - through the study of blood hormones, to diagnose diseases of the endocrine glands.

Definition of endocrine gland

Endocrine gland- a clearly defined macroanatomical structure, the main function of which is the synthesis of biologically active substances called hormones. In clinical endocrinology, seven endocrine glands are distinguished, the functions of which are assessed by studying the hormones produced by the gland in the blood. To assess its functions, not the entire spectrum of gland hormones is used, but a strictly limited set of them, with the help of which the function of the endocrine gland is determined. In addition to hormones, their metabolites can be used to diagnose diseases, which sometimes turn out to be a more reliable marker of endocrine disease than the study of the hormones themselves. Thus, in the diagnosis of pheochromocytoma, the study of catecholamine metanephrine metabolites is more reliable than adrenaline and norepinephrine.

The study of hormones for the diagnosis of endocrine diseases is not always justified. The most striking example is diabetes mellitus, the diagnosis of which does not use insulin testing, although the disease is caused by insulin deficiency. Also, the study of oxytocin and vasopressin is not used to diagnose their insufficient or excessive secretion, and a violation of their synthesis is determined by their metabolic effects.

Moreover, in the diagnosis of endocrine diseases, hormones that are not synthesized by the endocrine glands can be used, for example, insulin-like growth factor I (IGF-I), which is formed in the liver under the influence of growth hormone. It is used to diagnose acromegaly caused by a pituitary tumor.

Hormone synthesis by the endocrine gland can be:

its only function (for example, the anterior lobe of the pituitary gland);
combined with the generation of germ cells (for example, ovaries and testicles);
combined with exocrine secretion (for example, pancreas);
combined with the deposition of hormones synthesized outside of it.

The endocrine gland is capable of synthesizing:

the only hormone that is rare (for example, the parathyroid gland);
spectrum of hormones (usually):

specialized cellular substructures, in particular in the adrenal glands, two cellular substructures - the cortex and the medulla - produce steroid hormones and catecholamines, respectively;
by individual cells, united or not in isolated complexes, for example, in the pituitary gland, certain hormones are synthesized by individual cells that are not united into distinct cellular formations; In the pancreas, insulin and glucagon are produced by β- and α-cells united in the islets of Langerhans.

Nature and functions of hormones

Hormones are divided into two main groups.

Polypeptides or amino acid derivatives (most):

complex polypeptides (LH, hCG);
medium-sized peptides;
small peptides;
dipeptides (T 4 and T 3);
derivatives of individual amino acids (serotonin, histamine).

Cholesterol derivatives are two types of steroids:

with an intact steroid ring (adrenal and gonadal steroids);
with disconnected ring B.

There are four main functions of hormones in the body:

reproduction;
growth and development;
production, utilization and conservation of energy.

A single hormone, on the one hand, can have different biological effects on different organs, and in the same organ at different times; on the other hand, some biological processes are under the integral control of several hormones.

Hormones regulate the functions of the following targets:

other endocrine glands (eg, pituitary-adrenal connection);
functional systems;
organs (for example, T 4 and heart function or T 4 and brain function);
tissues (for example, cortisol and bone tissue).

Synthesis, storage and secretion of hormones

Peptide hormones are synthesized by the same mechanism as any other proteins. Often, a large prohormone molecule is synthesized first, which is then converted into a smaller hormone. For example, preproparathyroid hormone → proparathyroid hormone → parathyroid hormone. On the other hand, steroids and catecholamines are synthesized from smaller molecules.

Endocrine organs are not a unique site for the synthesis of hormones, however, only in them the synthesis of hormones and its regulation occur most effectively. Three main features distinguish an endocrine organ from non-endocrine tissue that synthesizes a hormone:

the rate of synthesis is much higher in the endocrine organ;
endocrine glands are equipped with a mechanism for transporting the hormone into the blood, which is usually regulated.

The rate of secretion of a hormone by a gland is determined by the rate of its synthesis, which can be regulated by other hormones that are tropic in relation to this gland. With the exception of T 4 and 1,25-dihydroxycholecalciferol, the body's reserves of hormones are very limited.

Stimulation of hormone secretion is associated with depolarization of the cell membrane and the opening of calcium channels, which leads to the entry of calcium into the cell, where it combines with calcium-binding protein.

Transport and elimination of hormones

Hormones are eliminated from the blood as a result of metabolic processes, for example, peptide hormones are inactivated by proteolytic enzymes. In the liver, hormones combine with glucuronic acid and are secreted into bile, but are partially reabsorbed, entering the so-called enterohepatic cycle. Hormones are also excreted in the urine.

Small molecules of hormones (T 4, in particular) bind to blood proteins, which slows down their elimination from the blood and maintains a small pool of free hormone in the blood at the required level. Protein binding also facilitates the transport of fat-soluble steroids.

Hormonal receptors

Hormone receptors are cellular proteins that bind hormones.

Interaction with the hormone causes a conformational change in the receptor, which activates a specific cellular enzyme system, which actually realizes the characteristic effect of the hormone. When a hormone binds to a cell membrane receptor, so-called second messengers appear in the cytosol (the first is the hormone). In the cell nucleus, the hormone receptor complex binds to deoxyribonucleic acid (DNA) and regulates gene expression. The maximum effect of the hormone usually occurs when less than 50% of the receptors are bound. Free receptors freed from connection with the hormone return to the cytosol or to the cell membrane, where they continue to participate in the hormone-receptor interaction.

Steroid hormones are lipophilic, so they diffuse freely across the cell membrane and then bind to cytosolic receptor proteins.

T3 binds to nuclear receptor proteins, and the T 3 receptor complex, combining with DNA, stimulates the formation of messenger RNA. Often, steroid and thyroid hormones act synergistically, mutually enhancing specific effects (potentiating gene expression).

The number of cell membrane receptors and intracellular receptors changes, and the strength of their connection with the hormone also changes. The cells of the myometrium and mammary glands contain oxytocin receptors, the number of which increases under the influence of estrogens (up-regulation) and decreases under the influence of progesterone (down-regulation). The myocardium contains norepinephrine receptors (β 1), the number of which and the affinity for norepinephrine increases under the influence of thyroid hormones (T 3 / T 4).

Water-soluble hormones (monoamines, amino acids and peptides) bind to receptors in the membrane, which is saturated with lipids and therefore does not allow water-soluble hormones to diffuse freely through the membrane. In the hormonal response of a cell, water-soluble hormones are called the first messengers. In response to their interaction with the receptor inside the cell, the so-called second messengers are activated - cAMP, cyclic guanosine monophosphate, inositol triphosphate, calcium ions, diacylglycerol, etc. Calcium ions serve as a very important second messenger. The flow of calcium ions across the cell membrane into the cytosol is controlled by hormone-receptor communication, nerve stimuli, or modified by other second messengers.

The concentration of hormones in most cases is 10 -10 mol/l. In this case, the binding of one molecule to a membrane receptor leads to the formation of 10,000 cAMP molecules in the cell, and in this regard, cAMP acts as a molecular amplifier of the hormonal signal (10,000 times!). Phosphodiesterase destroys cAMP, so its inhibitors - theophylline and caffeine - act synergistically with hormones in which cAMP is the second messenger. cAMP stimulates catabolic processes - lipolysis, glycogenolysis (glucagon), gluconeogenesis and ketogenesis, insulin secretion to β-cells and the pancreas.

Let's list them in order from head to toe. So, the endocrine system of the body includes: the pituitary gland, pineal gland, thyroid gland, thymus (thymus gland), pancreas, adrenal glands, as well as the sex glands - testes or ovaries. Let's say a few words about each of them. But first, let's clarify the terminology.

The fact is that science identifies only two types of glands in the body - endocrine and exocrine. That is, the glands of internal and external secretion - because this is how these names are translated from Latin. Exocrine glands include, for example, sweat glands that come out into the pores! on the surface of the skin.

In other words, the exocrine glands of the body secrete the produced secretions on surfaces in direct contact with the environment. Typically, their products serve to bind, contain, and then remove molecules of potentially dangerous or useless substances. In addition, the layers that have fulfilled their purpose are eliminated by the body itself - as a result of the renewal of the cells of the outer covering of the organ.

As for the endocrine glands, they completely produce substances that serve to start or stop processes inside the body. The products of their secretion are subject to constant and complete use. Most often with the disintegration of the original molecule and its transformation into a completely different substance. Hormones (the so-called secretion products of endocrine glands) are always in demand in the body because, when used as intended, they break down to form other molecules. That is, not a single hormone molecule can be reused by the body. Therefore, the endocrine glands normally must work continuously, often with uneven load.

As we see, in relation to the endocrine system the body has a kind of conditioned reflex. An excess or, on the contrary, a deficiency of any hormones is unacceptable here. In itself, fluctuations in the level of hormones in the blood are quite normal. It all depends on what process needs to be activated now and how much it needs to be done. The decision to stimulate or suppress any process is made by the brain. More precisely,* the neurons of the hypothalamus surrounding the pituitary gland. They give a “command” to the pituitary gland, and it begins, in turn, to “manage” the work of the glands. This system of interaction between the hypothalamus and the pituitary gland is called in medicine hypothalamic-pituitary.

Naturally, situations in a person’s life are different. And they all affect the condition and functioning of his body. And the brain—more precisely, its cortex—is responsible for the reaction and behavior of the body in certain circumstances. It is designed to ensure the safety and stability of the body under any external conditions. This is the essence of his daily work.

Thus, during a period of prolonged fasting, the brain must take a number of biological measures that would allow the body to wait out this time with minimal losses. And during periods of satiety, on the contrary, he must do everything to ensure that food is absorbed as completely and quickly as possible. Therefore, a healthy endocrine system is able, so to speak, to release huge single doses of hormones into the blood, so to speak, when necessary. And tissue brushes, in turn, have the ability to absorb these stimulants in unlimited quantities. Without this combination, the effective functioning of the endocrine system loses its main meaning.

If we now understand why a one-time overdose of a hormone is a phenomenon in principle impossible, let’s talk about the hormones themselves and the glands that produce them. Inside the brain tissue there are two glands - the pituitary gland and the pineal gland. Both of them are located inside the midbrain. The pineal gland is in its part, which is called the epithalamus, and the pituitary gland is in the hypothalamus.

Pineal gland produces mainly corticosteroid hormones. That is, hormones that control the activity of the cerebral cortex. Moreover, pineal gland hormones regulate the degree of its activity depending on the time of day. The tissues of the pineal gland contain special cells - pinealocytes. The same cells are found in our skin and retina. Their main purpose is to record and transmit information about the level of illumination outside to the brain. That is, about the amount of light that falls on them at a given time. And pinealocytes in the tissues of the pineal gland serve this gland so that it can alternately increase the synthesis of either serotonin or melatonin.

Serotonin and melatonin are the two main hormones of the pineal gland. The first is responsible for concentrated, uniform activity of the cerebral cortex. It stimulates attention and thinking that is not stressful, but as if normal for the brain during wakefulness. As for melatonin, it is one of the sleep hormones. Thanks to it, the speed of impulses passing through the nerve endings decreases, many physiological processes slow down and the person becomes sleepy. Thus, the periods of wakefulness and sleep of the cerebral cortex depend on how accurately and correctly the pineal gland distinguishes the time of day.

Pituitary, as we have already found out, performs many more functions than the pineal gland. In general, this gland itself produces more than 20 hormones for various purposes. Due to the normal secretion of all its substances by the pituitary gland, it can partially compensate for the functions of the glands of the endocrine system subordinate to it. With the exception of the thymus and islet cells in the pancreas, since these two organs produce substances that the pituitary gland cannot synthesize.

Plus, with the help of the products of its own synthesis, the pituitary gland still has time, so to speak, to coordinate the activities of the rest of the endocrine glands of the body. Processes such as the peristalsis of the stomach and intestines, the feeling of hunger and thirst, heat and cold, the rate of metabolism in the body, the growth and development of the skeleton, puberty, the ability to conceive, the rate of blood clotting, etc., depend on its correct operation. and so on.

Sustained dysfunction of the pituitary gland leads to large-scale disorders throughout the body. In particular, due to damage to the pituitary gland, diabetes mellitus may develop, which in no way depends on the condition of the pancreas tissue. Or chronic digestive dysfunction with an initially completely healthy gastrointestinal tract. Injuries to the pituitary gland significantly increase the clotting time of some blood proteins.

Next on our list thyroid. It is located in the upper front of the neck, just under the chin. The thyroid gland is shaped like a butterfly, much more than a shield. Because it is formed, like most glands, by two large lobes connected by an isthmus of the same tissue. The main purpose of the thyroid gland is to synthesize hormones that regulate the rate of metabolism of substances, as well as the growth of cells of all tissues of the body, including bone.

In most cases, the thyroid gland produces hormones formed with the participation of iodine. Namely, thyroxine and its more active modification from a chemical point of view - triiodothyronine. In addition, some thyroid cells (parathyroid glands) synthesize the hormone calcitonin, which serves as a catalyst for the reaction in the absorption of calcium and phosphorus molecules by the bones.

Thymus located slightly lower - behind the flat sternum bone, which connects two rows of ribs, forming our chest. The thymus lobes are located under the upper part of the sternum - closer to the collarbones. More precisely, where the common larynx begins to bifurcate, turning into the trachea of the right and left lungs. This endocrine gland is an essential part of the immune system. It produces not hormones, but special immune bodies - lymphocytes.

Lymphocytes, unlike leukocytes, are transported into tissues through lymph flow rather than blood flow. Another important difference between thymic lymphocytes and bone marrow leukocytes is their functional purpose. Leukocytes are not able to penetrate into the tissue cells themselves. Even if they are infected. Leukocytes are only capable of recognizing and destroying pathogens whose bodies are located in the intercellular space, blood and lymph.

It is not white blood cells that are responsible for the timely detection and destruction of infected, old, malformed cells, but lymphocytes that are produced and trained in the thymus. It should be added that each type of lymphocyte has its own not strict, but obvious “specialization”. Thus, B lymphocytes serve as unique indicators of infection. They detect the pathogen, determine its type and trigger the synthesis of proteins directed specifically against this invasion. T lymphocytes regulate the speed and strength of the immune system's response to infection. And NK lymphocytes are indispensable in cases where it is necessary to remove from tissues cells that are not affected by infection, but defective ones that have been exposed to irradiation or the action of toxic substances.

Pancreas located where indicated< в ее названии, - под сфинктером желудка, у начал а тонкого кишечника. В основном своем назначении она вырабатывает пищеварительные ферменты тонкого кишечника. Однако в массиве ее тканей имеются включения клеток другого типа, которые вырабатывают всем известный гормон инсулин. Инсулином он был назван потому, что группки производящих его клеток по виду напоминают островки. А в переводе с латинского языка слово insula и означает «остров».

It is known that all substances received with food are broken down in the stomach and intestines into glucose molecules - the main source of energy for any cell in the body.

The absorption of glucose by cells is possible only in the presence of insulin. Therefore, if there is a deficiency of this pancreatic hormone in the blood, a person eats, but his cells do not receive this food. This phenomenon is called diabetes mellitus.

Next: down we have the adrenal glands. If the kidneys themselves act as the main filters of the body and synthesize urine, then the adrenal glands are completely busy producing hormones. Moreover, in terms of the direction of action, the hormones produced by the adrenal glands largely duplicate the work of the pituitary gland. Thus, the adrenal body is one of the main sources of stress hormones - dopamine, norepinephrine and adrenaline. And their bark is a source of corticosteroid hormones aldosterone, cortisol (hydrocortisone) and corticosterone. Among other things, in the body of each person the adrenal glands synthesize a nominal amount of hormones of the opposite sex. In women it is testosterone, and in men it is estrogen.

And finally, gonads. Their main purpose is obvious, and it consists in the synthesis of a sufficient amount of sex hormones. Sufficient for the formation of an organism with all the signs of its gender and for the further uninterrupted operation of the reproduction system. The difficulty here lies in the fact that the body of both men and women simultaneously produces hormones of not one, but both sexes. Only the main hormonal background is formed due to the work of the gonads of the corresponding type (ovaries or testes), and the secondary one - due to the much lesser activity of other glands.

For example, in women, testosterone is produced primarily in the adrenal glands. And estrogen in men is found in the adrenal glands and fat deposits. The ability of fat cells to synthesize substances with properties resembling hormones was discovered relatively late - in the 1990s. Until this time, adipose tissue was considered an organ that took minimal part in metabolism. Their role was assessed by science very simply - fat was considered a place of accumulation and storage of female sex hormones estrogen. This explained the high percentage of fatty tissue in a woman’s body compared to men.

At present, the understanding of the biochemical role of adipose tissue in the body has expanded significantly. This happened thanks to the discovery of adipokines - hormone-like substances that are synthesized by fat cells. There are quite a lot of these substances, and their study has only just begun. Nevertheless, we can already say with confidence that among the adipokines there are substances that can increase the resistance of body cells to the action of the body’s own insulin.

So, we already know that the endocrine system of the body includes seven endocrine glands. And, as we ourselves could see, there are strong relationships between them. Most of these relationships are formed by two factors. The first is that the work of all endocrine glands is coordinated and controlled by a common analytical center - the pituitary gland. This gland is located inside the brain tissue, and its work, in turn, is regulated by this organ. The latter becomes feasible due to the presence of a separate system of connections between the neurons of the hypothalamus and the cells of the pituitary gland, which is called the hypothalamic-pituitary.

And the second factor is the effect that we have clearly demonstrated of duplicating the functions of many glands with each other. For example, the same pituitary gland not only regulates the activity of all elements of the endocrine system, but also synthesizes most of the same substances as they do. Likewise, the adrenal glands produce a number of hormones that will be sufficient to continue the functioning of the cerebral cortex. Including complete failure of both the pituitary gland and the pineal gland. In the same way, the adrenal glands are capable of changing the content of the body’s basic hormonal levels in the event of failure of the gonads. This will happen due to their ability to produce hormones of the opposite sex.

As mentioned above, the exception to this system of mutually determined connections are two glands - the thymus and special cells in the pancreas that produce insulin. However, there are no truly strict exceptions here either. Lymphocytes produced in the thymus form a very important part of the body's immune defense. However, we understand that we are talking about only part of immunity, and not about it as a whole. As for islet cells, in fact, the mechanism of sugar absorption with the help of insulin in the body is not the only one. The liver and brain are organs that are able to metabolize glucose even in the absence of this hormone. The only “but” is that the liver is only capable of processing a slightly different chemical modification of glucose, called fructose.

Thus, in the case of the endocrine system, the main difficulty is that most pathologies and medical influences simply cannot affect only one, the target organ. This is impossible because both similar cells in other glands and the pituitary gland, which records the level of each hormone in the patient’s blood, will necessarily react to such an effect.

The endocrine system is one of the most important in the body. It includes organs that regulate the activity of the entire body through the production of special substances - hormones.

This system ensures all vital processes, as well as the body’s adaptation to external conditions.

It is difficult to overestimate the importance of the endocrine system; the table of hormones secreted by its organs shows how wide the range of their functions is.

The structural elements of the endocrine system are the endocrine glands. Their main task is the synthesis of hormones. The activity of the glands is controlled by the nervous system.

The endocrine system consists of two large parts: central and peripheral. The main part is represented by brain structures.

This is the main component of the entire endocrine system - the hypothalamus and its subordinate pituitary and pineal glands.

The peripheral part of the system includes glands located throughout the body.

These include:

thyroid;
parathyroid glands;
thymus;
pancreas;
adrenal glands;
gonads.

Hormones secreted by the hypothalamus act on the pituitary gland. They are divided into two groups: liberins and statins. These are the so-called releasing factors. Liberins stimulate the pituitary gland to produce its own hormones, while statins slow down this process.

The pituitary gland produces tropic hormones, which, entering the bloodstream, are carried to the peripheral glands. As a result, their functions are activated.

Disturbances in the functioning of one of the links of the endocrine system entail the development of pathologies.

For this reason, when diseases appear, it makes sense to get tested to determine hormone levels. These data will help prescribe effective treatment.

Table of glands of the human endocrine system

Each organ of the endocrine system has a special structure that ensures the secretion of hormonal substances.

Gland	Localization	Structure	Hormones
Hypothalamus	It is one of the divisions of the diencephalon.	It is a collection of neurons that form the hypothalamic nuclei.	The hypothalamus synthesizes neurohormones, or releasing factors, which stimulate the activity of the pituitary gland. Among them are gandoliberins, somatoliberin, somatostatin, prolactoliberin, prolactostatin, thyreoliberin, corticoliberin, melanoliberin, melanostatin. The hypothalamus secretes its own hormones - vasopressin and oxytocin.
Pituitary	This small gland is located at the base of the brain. The pituitary gland is connected by a stalk to the hypothalamus.	The gland is divided into lobes. The anterior part is the adenohypophysis, the posterior part is the neurohypophysis.	The adenohypophysis synthesizes somatotropin, thyrotropin, corticotropin, prolactin, and gonadotropic hormones. The neurohypophysis serves as a reservoir for the accumulation of oxytocin and vasopressin coming from the hypothalamus.
Epiphysis (pineal body)	The pineal gland is a small formation in the diencephalon. The gland is located between the hemispheres.	The pineal body consists primarily of parenchyma cells. Its structure contains neurons.	The main hormone of the pineal gland is serotonin. Melatonin is synthesized from this substance in the pineal gland.
Thyroid	This organ is located in the neck area. The gland is located under the larynx next to the trachea.	The gland is shaped like a shield or butterfly. The organ consists of two lobes and an isthmus connecting them.	Thyroid cells actively secrete thyroxine, triiodothyronine, calcitonin, and thyrocalcitonin.
Parathyroid glands	These are small structures located near the thyroid gland.	The glands are round in shape. They consist of epithelial and fibrous tissue.	The only hormone produced by the parathyroid glands is parathyroid hormone, or parathyroid hormone.
Thymus (thymus gland)	The thymus is located at the top behind the sternum.	The thymus gland has two lobes that widen downward. The consistency of the organ is soft. The gland is covered with a sheath of connective tissue.	The main hormones of the thymus are thymulin, thymopoietin and thymosin of several fractions.
Pancreas	The organ is located in the abdominal cavity near the stomach, liver and spleen.	The gland has an elongated shape. It consists of a head, body and tail. The structural unit is the islets of Langerhans.	The pancreas secretes somatostatin, insulin, and glucagon. This organ is also part of the digestive system due to the production of enzymes.
Adrenal glands	These are paired organs located directly above the kidneys.	The adrenal glands have a medulla and a cortex. Structures perform different functions.	The medulla secretes catecholamines. This group includes adrenaline, dopamine, norepinephrine. The cortical layer is responsible for the synthesis of glucocorticoids (cortisol, corticosterone), aldosterone and sex hormones (estradiol, testosterone).
Ovaries	The ovaries are the female reproductive organs. These are paired formations located in the small pelvis.	Follicles are located in the cortex of the ovaries. They are surrounded by stroma - connective tissue.	Progesterone and estrogen are synthesized in the ovaries. The levels of both hormones are variable. It depends on the phase of the menstrual cycle and a number of other factors (pregnancy, lactation, menopause, puberty).
Testicles (testes)	This is a paired organ of the male reproductive system. The testicles are lowered into the scrotum.	The testicles are permeated with convoluted tubules and covered with numerous membranes of fibrous origin.	The only hormone produced in the testes is testosterone.

The following topic will be useful for everyone: . Everything about the structure and functions of the pancreas in the human body.

Table of endocrine hormones

All hormones secreted by the central and peripheral endocrine glands are of a different nature.

Some of them are derivatives of amino acids, others are polypeptides or steroids.

For more information about the nature of hormones and their functions, see the table:

Hormone	Chemical nature	Functions in the body
Folliberin	Chain of 10 amino acids	Stimulation of the secretion of follicle-stimulating hormone.
Luliberin	10 amino acid protein	Stimulation of luteinizing hormone secretion. Regulation of sexual behavior.
Somatiliberin	44 amino acids	Increases the secretion of growth hormone.
Somatostatin	12 amino acids	Reduces the secretion of somatotropic hormone, prolactin and thyroid-stimulating hormone.
Prolactoliberin	Polypeptide	Stimulation of prolactin production.
Prolactostatin	Polypeptide	Decreased prolactin synthesis.
Thyroid hormone	Three amino acid residues	Provokes the production of thyroid-stimulating hormone and prolactin. It is an antidepressant.
Corticoliberin	41 amino acids	Enhances the production of adenocorticotropic hormone. Affects the immune and cardiovascular systems.
Melanoliberin	5 amino acid residues	Stimulates the secretion of melatonin.
Melanostatin	3 or 5 amino acids	Inhibits the secretion of melatonin.
Vasopressin	Chain of 9 amino acids	Participates in the memory mechanism, regulates stress reactions, kidney and liver function.
Oxytocin	9 amino acids	Provokes uterine contractions during childbirth.
Somatotropin	Polypeptide of 191 amino acids	Stimulates the growth of muscle, bone and cartilage tissue.
Thyrotropin	Glycoprotein	Activates the production of thyroxine by the thyroid gland.
Corticotropin	39 amino acid peptide	Regulates the process of lipid breakdown.
Prolactin	Polypeptide of 198 amino acid residues	Stimulates lactation in women. Increases the intensity of testosterone secretion in men.
Luteinizing hormone	Glycoprotein	Strengthens the secretion of cholesterol, androgens, progesterone.
Follicle stimulating hormone	Glycoprotein	Provokes the growth and development of follicles in women, increases the synthesis of estrogen. In men, it ensures the growth of the testes.
Serotonin	Biogenic amine	Affects the circulatory system, participates in the formation of allergic reactions and pain.
Melatonin	Derivative of the amino acid tryptophan	Stimulates the process of formation of pigment cells.
Thyroxine	Derivative of the amino acid tyrosine	Accelerates redox processes and metabolism.
Triiodothyronine	An analogue of thyroxine containing iodine atoms	Affects the nervous system, ensuring normal mental development.
Calcitonin	Peptide	Promotes calcium storage.
Parathyroid hormone	Polypeptide	Forms bone tissue, participates in the exchange of phosphorus and calcium.
Timulin	Peptide	Activates or inhibits the activity of lymphocytes.
Thymopoietin	49 amino acids	Participates in the differentiation of lymphocytes.
Thymosin	Protein	Forms immunity and stimulates the development of the musculoskeletal system.
Insulin	Peptide	Regulates carbohydrate metabolism, in particular reduces the level of simple sugars.
Glucagon	29 amino acid residues	Increases glucose concentration.
Adrenalin	Catecholamine	Increases heart rate, dilates blood vessels, relaxes muscles.
Norepinephrine	Catecholamine	Increases blood pressure.
Dopamine	Catecholamine	Increases the strength of heart contractions and increases systolic pressure.
Cortisol	Steroid	Regulates metabolic processes and blood pressure.
Corticosterone	Steroid	Inhibits the synthesis of antibodies and has an anti-inflammatory effect.
Aldosterone	Steroid	Regulates salt exchange, retains water in the body.
Estradiol	Cholesterol derivative	Supports the processes of gonad formation.
Testosterone	Cholesterol derivative	It provokes protein synthesis, ensures muscle growth, and is responsible for spermatogenesis and libido.
Progesterone	Cholesterol derivative	Provides optimal conditions for conception and supports gestation.
Estrogen	Cholesterol derivative	Responsible for puberty and the functioning of the reproductive system.

The variety of structural options provides a wide range of functions performed by hormones. Insufficient or excessive secretion of any of the hormones leads to the development of pathologies. The endocrine system controls the activity of the entire body at the hormonal level.