The role of the parathyroid gland in the human body. Parathyroid gland, its hormones and functions

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Parathyroid(parathyroid) glands are located on the posterior surface of the thyroid gland outside its capsule near the upper and lower poles, have a round shape, a diameter of up to 5 mm, and a weight of up to 0.5 g. Usually a person has 2 pairs of parathyroid glands (upper and lower). The number and location of parathyroid glands (PTG) can vary significantly, sometimes reaching up to 12 pairs. Additional parathyroid glands are found in the tissue of the thyroid and thymus glands, in the anterior and posterior mediastinum, in the pericardium, behind the esophagus, in the area of the bifurcation of the common carotid artery. The blood supply to the parathyroid gland is carried out mainly by the branches of the thyroid artery, and therefore damage to these glands is possible during operations on the thyroid gland.

The parenchyma of the glands consists of parathyrocytes, among which the main cells, stained with basic dyes, and oxyphilic cells are distinguished. The main parathyroid cells are hormonally active cells that are divided into light cells, which predominate in children, and dark cells, which predominate in adults. Oxyphilic parathyroid cells (“resting” cells) appear at the age of 10 years, they are hormonally inactive.

The main hormone of the parathyroid gland is parathyroid hormone, which is formed in the parathyroid glands from the precursors of preproparathyroid hormone and proparathyroid hormone. The biological activity of human parathyroid hormone is associated with fragments 1-29, 1-34 and 53-84 of its amino acid chain. The hormone circulates in the blood in three main forms: intact parathyroid hormone with a molecular weight of 9500, a biologically active carboxyl fragment with a molecular weight of 7000-7500, a biologically active fragment with a molecular weight of 4000. The formation of fragments occurs in the liver and kidneys. The action of parathyroid hormone is mediated by the adenylate cyclase system of target cells.

Parathyroid hormone takes part in maintaining calcium homeostasis; when its level decreases, hormone secretion is stimulated, and when its level increases, it is inhibited. With an increased need for calcium, the function of the pancreas increases (Fig. 1).

Rice. 1. Regulation of calcium metabolism

By acting directly on osteoclasts, parathyroid hormone promotes release of calcium salts from bone tissue, while the level of calcium and phosphorus in the blood increases. Under the influence of parathyroid hormone, the number and activity of osteoclasts increase as a result of its direct effect on osteoblast receptors that produce local tissue factors that activate osteoclast precursor cells. The effects of short-term and long-term effects of parathyroid hormone on bone are different: short intermittent action leads to bone formation, long-term continuous action leads to destruction. With an excess of parathyroid hormone, a negative bone balance occurs (decreased bone density), which is accompanied by excessive release of hydroxyproline.

By acting on the renal tubules, parathyroid hormone reduces phosphate reabsorption, causing phosphaturia. In addition, the indirect effect of parathyroid hormone on phosphorus-calcium metabolism is associated with its activating effect on 1α-hydroxylase of the renal tubules, as a result of which 25-hydroxycholecalciferol is converted into active 1,25-dioxycholecalciferol.

Calcitriol acts on calcium reservoirs as a parathyroid hormone synergist. Its action is primarily aimed at increasing the absorption of calcium in the intestine and enhancing its reabsorption in the renal glomeruli. Cholecalciferol (vitamin D3) is formed in the skin (Malpighian layer of the epidermis) from 7-dehydrocholesterol under the influence of ultraviolet rays (Fig. 2).

Rice. 2. Synthesis and metabolism of vitamin D3

Next, cholecalciferol binds to D-binding protein and enters the liver. In the liver, cholecalciferol is converted by 25-hydroxylase to 25-hydroxycholecalciferol (25-OH-D3), the main form in which this vitamin circulates in the bloodstream in association with the same D-binding protein. In the proximal convoluted renal tubules, under the action of 1α-hydroxylase, 25-hydroxycholecalciferol is hydroxylated at the C1 position, turning into biologically active 1,25-dioxycholecalciferol. An increase in the level of calcitriol in plasma inhibits the activity of 1α-hydroxylase and increases the activity of 24-hydroxylase, which leads to the predominant formation of 25-OH-D3 not 1,25-(OH)2-D3, but the by-product 24,25-(OH )2-D3, which has no biological activity. The action of l,25-(OH)2-D3 at the cellular level is similar to that of other steroid hormones.

It also plays an important role in the regulation of calcium metabolism. calcitonin- a hormone produced by the C cells of the thyroid gland. Calcitonin is a peptide consisting of 32 amino acids. By inhibiting the activity of osteoclasts, calcitonin inhibits the resorption of the bone matrix and thereby causes the release of calcium and phosphate. The production of calcitonin and parathyroid hormone is inversely related. The main stimulator of calcitonin secretion is an increase in the concentration of ionized calcium in the blood, an inhibitor of a decrease in calcium levels. It should be noted that removal of the thyroid gland (with parafollicular cells) in humans and animals does not lead to hypercalcemia, and the administration of calcitonin to healthy individuals does not lead to a decrease in calcium levels in the blood.

Normally a person consumes about 1 gram calcium per day. From 25 to 50% of calcium is absorbed with the participation of 1,25-dioxycholecalciferol. Blood plasma contains calcium in two main forms. The fraction of calcium bound to albumin accounts for slightly less than half of the total amount of calcium determined by routine methods. The fraction of free (ionized) calcium is biologically active. Hypocalcemia stimulates the synthesis of parathyroid hormone, which enhances the resorption of calcium from bone tissue into the blood and the excretion of phosphorus in the urine, which allows maintaining a normal calcium-to-phosphorus ratio.

The bulk (99%) of calcium available in the body is found in the bones. Bone is a constantly updating dynamic system, where remodeling processes occur throughout life: destruction of old bone - bone resorption and formation of new bone - bone formation. Bone tissue consists of cellular elements, intercellular substance - bone matrix and mineral components. Bone tissue contains the following cells: osteoblasts with the ability for protein synthesis, osteoclasts, which absorb bone tissue due to lysosomal enzymes; osteocytes- metabolically inactive cells located in lacunae deeply embedded in the bone; Osteocytes originate from osteoblasts embedded in their own bone matrix.

Process bone remodeling is divided into 5 phases (Fig. 3). In a healthy adult body, up to 80% of trabecular and 95% of cortical bone tissue is in the resting phase. Activation phase, which occurs in each bone site with an interval of 2-3 years, includes the proliferation and activation of osteoclast precursors, the entry and attachment of multinuclear osteoclasts to the surface of the resorbed site. Followed by resorption phase, which lasts about 1-3 weeks. This process consists of melting the inorganic bone matrix with subsequent degradation of the organic one, which is ensured by the entry of hydrogen ions and lysosomal enzymes of osteoclasts into the resorption sites. Transition phase lasts 1-2 weeks, while osteoblasts appear in the resorbed cavity. New bone formation begins with the deposition of bone matrix by osteoblasts at a rate of 2-3 microns per day, which mineralizes after 5-10 days. The process of bone formation lasts about 3 months, and the full cycle of bone renewal in each area takes 4-8 months. Overall bone turnover is approximately 4-10% annually.

The parathyroid glands are clusters of endocrine cells and perform the function of controlling phosphorus-calcium metabolism in the body. Various internal or external factors can lead to disruption of these glands. Pathological changes are manifested by characteristic symptoms, the main one of which is excessive or insufficient amounts of trace elements in the blood. Both traditional drug therapy and surgical intervention are used to treat endocrine disorders.

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Functions of the parathyroid gland in the body

The parathyroid (parathyroid) gland is a collection of endocrine cells. In a healthy person, it is presented in the form of several glandular formations, usually from 2 to 8, and they are located on the back side of the thyroid capsule, near the vascular-cervical bundle and the esophagus.

Anatomy of the parathyroid glands

The parathyroid gland plays a vital role in the body, regulating calcium-phosphorus metabolism. Its main function is the production of specialized parathyroid hormone, which controls the level of phosphorus and calcium in the blood. The parathyroid glands are responsible for the normal functioning of the central nervous system, bone tissue and musculoskeletal system.

Functions of the parathyroid gland

Metabolic processes are controlled according to the following scheme:

1. The glands are equipped with specialized receptors that determine the content of trace elements in the blood.
2. If the calcium content is reduced, the organ’s functioning is activated, resulting in increased secretion of parathyroid hormone. In this situation, the release of the required amount of calcium from bone tissue is stimulated.
3. If the concentration is excessively high, calcitonin is secreted, which helps reduce calcium levels and normalize the metabolism of microelements.

Causes of violations

The parathyroid glands are closely related to the thyroid gland and are responsible for the normal course of numerous processes in the body. Various metabolic disorders are caused by several main reasons:

As a result, various disturbances in the functioning of the endocrine system and other health problems arise. This significantly reduces the quality of human life, as it contributes to a significant deterioration in well-being.

Symptoms of the development of pathologies

The main sign of malfunctioning of the parathyroid glands is disturbances in the metabolism of calcium and phosphorus. The symptoms of these changes are identical to the signs of the development of other diseases of the endocrine system:

excessive excitability of the nervous system;
constant feeling of weakness and fatigue;
convulsions;
decreased appetite;
depressed mood, state of depression, depressed mood;
frequent headaches.

Very often, disturbances in calcium-phosphorus metabolism cause deterioration in kidney function, which is accompanied by a constant feeling of thirst and the development of urolithiasis. The level of hemoglobin in the blood decreases. The patient may experience a persistently elevated body temperature. In women, the symptoms of the disease are more pronounced, since they exhibit external signs of parathyroid disorders in the early stages:

strands become brittle and dull;
nails become split and thin;
constantly want to sleep, which is accompanied by a general feeling of weakness;
teeth deteriorate;
vision deteriorates, cataracts may develop, or calcium salts may be deposited on the cornea;
eyebrows and eyelashes fall out;
dermatological diseases occur - eczema, psoriasis;
the skin becomes very dry and acquires a yellow tint.

Types of diseases

Disturbances in the functioning of the parathyroid glands, which are responsible for calcium-phosphorus metabolism, can manifest themselves in two main diseases:

hyperparathyroidism;
hypoparathyroidism.

Hyperparathyroidism

Hyperparathyroidism is an endocrinopathy caused by hyperfunction of the glands that produce excess amounts of parathyroid hormone. With this pathology, an increase in the amount of calcium in the blood is observed. The first changes characteristic of hyperparathyroidism concern bone tissue, gonads and kidneys. According to statistics, women suffer from this disease three times more often than men. The disease is mainly diagnosed between the ages of 25 and 50 years.

Symptoms of hyperparathyroidism

In most situations, the main cause of organ hyperfunction is the occurrence of a benign tumor in the body (hyperparathyroid adenoma). Since the neoplasm affects the entire gland, and its size is constantly increasing, this activates excessive production of the hormone in the blood. At the same time, the functions of controlling the amount of calcium are weakened. Timely comprehensive treatment, including both drug therapy and surgical removal of the organ, guarantees complete relief from the disease.

Hypoparathyroidism

Hypoparathyroidism is a pathology caused by hypofunction of the parathyroid glands. With this disorder, parathyroid hormone is produced by the organ in insufficient quantities, which leads to a significant decrease in the level of calcium in the blood. The disease has specific symptoms - increased excitability of the muscles and nervous system. The main reasons for the development of hypoparathyroidism are the influence of such factors:

The first sign of the development of this pathology is symmetrical, regular and very painful muscle spasms. If hypoparathyroidism progresses, muscle tissue can completely atrophy, which is accompanied by a feeling of numbness in the arms and legs, with increasing intensity. Secondary symptoms of the disorder include the following:

memory deteriorates;
neuroses and depressive states arise;
the patient is haunted by a constant feeling of weakness;
the excitability of the nervous system increases.

Symptoms can manifest themselves in different ways, depending on various external influences, such as excessively high or low air temperatures, stressful conditions, physical activity, and infectious diseases. So that the doctor can make a correct diagnosis, the patient takes a blood test to determine the amount of parathyroid hormone, phosphorus and calcium. X-rays are used as an additional diagnostic method for suspected hypoparathyroidism, which helps detect changes in bone tissue. Hypoparathyroidism poses the greatest danger to children, as it can cause physiological and mental abnormalities, as well as mental problems.

Diagnostics

The main methods for diagnosing diseases of the parathyroid glands are blood and urine tests to determine the content of microelements. Additional research methods are:

1. Ultrasound (ultrasound examination)– determines the presence of tissue hypo- or hyperplasia.
2. CT scan– helps to make a diagnosis with an accuracy of up to 95%, as it reliably identifies disorders in the parathyroid glands, other organs and bone tissue.
3. Magnetic resonance imaging– is characterized by maximum safety for patients, as well as information content.
4. X-ray– helps determine the presence of pathologies of the heart, blood vessels and bone tissue.
5. Histology– tissue research.

Each of the above types of diagnostics has its own advantages. As a rule, specialists simultaneously prescribe several different research methods to most accurately determine the causes of the disease and prevent its development.

Treatment

To treat pathologies of the parathyroid glands, depending on the cause and severity of the disease, specialists can prescribe both drug therapy and surgical intervention.

Medication

Drug treatment consists of prescribing calcium preparations - gluconate or chloride. They also use a diet rich in this macronutrient. Patients are advised to consume dairy products, sea fish, cabbage, vegetables and fruits. Vitamin D is prescribed in combination with calcium, which promotes better absorption of the macronutrient. To increase the production of their own vitamin D, patients are advised to take sunbathing or attend sessions of special therapeutic ultraviolet irradiation.

To prevent the occurrence of seizures, bromine preparations and anticonvulsants - Luminal - are prescribed as prophylaxis. In case of severe hypocalcemia (crisis), calcium gluconate is administered intravenously.

Surgical intervention

In cases where the cause of the development of pathological changes is an adenoma, only surgical treatment is used. During the operation, specialists remove the tumor. The remaining glands are also examined to detect adenomas for their further removal. The gland itself, or a certain part of it, is removed extremely rarely. This is fraught with serious consequences - hypoparathyroidism and a decrease in calcium levels in the blood. The organ is completely removed if cancer is detected.

The most effective method of surgical intervention is organ transplantation, with full preservation of its functions. The damaged part of the parathyroid gland can also be transplanted if drug therapy is insufficient.

Despite the virtual absence of pronounced symptoms, parathyroid glandular disorders can lead to serious consequences for the body - disruptions in the normal functioning of the most important organs and systems. Therefore, it is mandatory for every person to undergo regular examination by an endocrinologist, and urgently consult a doctor when the first signs of disease appear.

The parathyroid glands (usually four) are located on the posterior surface of the thyroid gland and are separated from it by a capsule.

The functional significance of the parathyroid glands is the regulation calcium metabolism. They produce a protein hormone parathyrin, or parathyroid hormone, which stimulates bone resorption by osteoclasts, increasing calcium levels in the blood. Osteoclasts themselves do not have receptors for parathyroid hormone; its action is mediated by other bone tissue cells - osteoblasts.

In addition, parathyroid hormone reduces the excretion of calcium by the kidneys and also enhances the synthesis of the vitamin D metabolite, which, in turn, increases the absorption of calcium in the intestine.

Development. The parathyroid glands are formed in the embryo as protrusions from the epithelium of the III and IV pairs of gill pouches of the pharyngeal intestine. These protrusions are laced, and each of them develops into a separate parathyroid gland, and from the IV pair of gill pouches the upper pair of glands develops, and from the III pair the lower pair of parathyroid glands develops, as well as the thymus gland.

Structure of the parathyroid gland

Each parathyroid gland is surrounded by a thin connective tissue capsule. Its parenchyma is represented by trabeculae - epithelial strands of endocrine cells - parathyrocytes. The trabeculae are separated by thin layers of loose connective tissue with numerous capillaries. Although intercellular gaps are well developed between parathyrocytes, neighboring cells are connected by interdigitations and desmosomes. There are two types of cells: chief parathyrocytes and oxyphilic parathyrocytes.

Chief cells secrete parathyrin, they predominate in the parenchyma of the gland, are small in size and polygonal in shape. In the peripheral zones, the cytoplasm is basophilic, where clusters of free ribosomes and secretory granules are scattered. With increased secretory activity of the parathyroid glands, the main cells increase in volume. Among the main parathyroid cells, two types are also distinguished: light and dark. Glycogen inclusions are found in the cytoplasm of light cells. It is believed that light cells are inactive, and dark cells are functionally active parathyroid cells. The main cells carry out the biosynthesis and release of parathyroid hormone.

The second type of cells is oxyphilic parathyroid cells. They are small in number, located singly or in groups. They are much larger than the main parathyroid cells. In the cytoplasm, oxyphilic granules and a huge number of mitochondria are visible with weak development of other organelles. They are considered as senescent forms of chief cells. In children, these cells are rare, and their number increases with age.

The secretory activity of the parathyroid glands is not influenced by pituitary hormones. The parathyroid gland, using a feedback principle, quickly responds to the slightest fluctuations in the level of calcium in the blood. Its activity is enhanced by hypocalcemia and weakened by hypercalcemia. Parathyrocytes have receptors that can directly perceive the direct effects of calcium ions on them.

Innervation. The parathyroid glands receive abundant sympathetic and parasympathetic innervation. Unmyelinated fibers end in terminals in the form of buttons or rings between parathyroid cells. Around the oxyphilic cells, the nerve terminals take the form of baskets. Encapsulated receptors are also found. The influence of incoming nerve impulses is limited to vasomotor effects.

Age-related changes. In newborns and young children, only chief cells are found in the parenchyma of the parathyroid glands. Oxyphilic cells appear no earlier than 5-7 years, by which time their number is rapidly increasing. After 20-25 years, the accumulation of fat cells gradually progresses.

The human body is a complex structure in which the work of all organs is interconnected, and destructive disorders of one of them leads to an imbalance in the overall balance. The parathyroid gland belongs to the category of internal secretion and is part of the systems that organize metabolism in the body. Contrary to this, it was not known to medical science until the beginning of the 20th century.

What is the parathyroid gland?

The parathyroid gland is small in size, 4 - 8 mm, and 1 - 3 mm in height, round or oval in shape. The color depends on the age of the person, at first it is pinkish, over time it turns pale yellow.

Her body is covered with fibrous tissue through which blood feeds her. They are located on the front of the neck, in the upper and lower parts of the thyroid gland. Their number and location vary from person to person.

The typical arrangement of the parathyroid glands is in pairs. Normally there should be from 2 to 6 pairs. Usually there are 2 pairs, their location can be:

thymus
spine
esophageal wall
neurovascular cervical bundle

Variability in number and location makes organ detection difficult, which creates difficulties for surgeons during surgery.

Role in the body

For a long time, doctors had no idea about the existence of the parathyroid gland, and operations on the thyroid gland ended in death.

Traumatization or removal of these glands during surgery leads to a sharp decrease in calcium in the blood, since its main function is to maintain the phosphorus-calcium balance in the body. It affects nerve impulses and joints.

The regulation of calcium concentration is carried out through the production of a specific hormone - which consists of 84 amino acid residues. This organ has sensitive receptors that respond to fluctuations in calcium levels in the blood, and in accordance with the obtained values, regulates the level of hormone intake into the body.

It has an impact in three directions:

In the kidneys, it stores the active form of vitamin D in the kidneys. The intestinal walls produce more calmodulin, which stimulates the absorption of calcium into the blood.
Reduces calcium concentration in urine
Promotes the transfer of calcium from the bone structure to the blood.

Important! Parathyroid hormone has a dominant effect on phosphorus-calcium metabolism. Other mechanisms regulating balance are auxiliary.

The activity of the hormone varies depending on the time of day: in the light the concentration increases, in the dark it decreases. In addition, the hormones that the gland produces are involved in the transmission of nerve impulses to the muscles and ensure the proper formation of bone tissue.

Symptoms of parathyroid dysfunction and its diagnosis

Important! The main test that allows us to reliably judge the quality of the parathyroid gland is a blood test. It determines the content of parathyroid hormones.

The first manifestations of imbalance are identical to the symptoms of diseases of the endocrine system:

decreased performance
numbness of the limbs
blood pressure surges
increased irritability
depressive states

An imbalance in the production of parathyroid hormones affects the entire body, affecting all organs and systems with which they interact. They may manifest themselves by the development of diseases such as gout, cataracts, progressive arrhythmia, and urolithiasis.

Disturbances in hormone production affect a person’s appearance: hair becomes brittle, hair loss increases, skin diseases appear, nails and teeth deteriorate, and skeletal muscles become inflamed.

At the first suspicion of an imbalance in the functioning of the parathyroid gland, it is necessary to undergo an examination. Laboratory tests are mandatory: blood and urine are donated. Standard tests:

determination of calcium and phosphates in urine
parathyroid hormone levels
serum and ionized calcium levels

Important! The corridor for the normal value of calcium content in the body is quite narrow, so its regulation occurs non-stop. In healthy people, the value ranges from 10-55 picograms per 1 ml.

The most accurate results of diagnosing the condition of the gland are provided by instrumental methods. With their help, the presence of pathologies and the general functional state are determined.

Usually, doctors use several methods at once to increase the accuracy and double-check the results obtained, and make a diagnosis based on the generalized data.

Diseases

All diseases are associated with impaired production of parathyroid hormone. Their level may be excessive or, conversely, insufficient.

Hyperparathyroidism

Excessive amounts of the hormone are called hyperparathyroidism. This condition leads to an increase in the proportion of calcium in the blood and a decrease in bone tissue. In advanced cases of the disease, it can cause coma.

Everyone has heard about the thyroid gland, which, like a butterfly, is located on the neck. But few people know that behind each lobe of the thyroid gland there is a small paired parathyroid gland - its hormones take an active part in phosphorus-calcium metabolism and are also very important for the body. What is this organ and what biological role does it play? Let’s try to figure it out using the results of the latest medical research, photos and videos in this article.

Parathyroid glands (other names: parathyroid, parathyroid) are four small endocrine formations that are located on the posterior wall of the thyroid gland, in pairs at the lower and upper poles of the organ.

Glandulae parathyroideae are found on both lateral lobes of the thyroid gland, and in some cases they are all localized on one side. The parathyroid glands are immersed in loose tissue, which fills the space between the fascial sheath and the fibrous capsule of the thyroid gland; there are cases of their location outside the boundaries of the vagina.

Some anatomical characteristics of the organ are indicated in the following table:

The level of location of the upper pair of parathyroid glands, as a rule, is the border of the middle and upper 1/3 of the posteromedial surfaces of each lateral lobe of the thyroid gland and the lower edge of the cricoid cartilage.

As for the lower pair, the glands belonging to it are larger in size compared to the upper ones and are located on the posterolateral surface of the lower 1/3 of each lateral lobe, 5–10 mm of the lower edge. In some cases, they are immersed in the tissue surrounding the thyroid gland from below.

Interesting! Both the upper and lower pairs of glandulae parathyroideae are located asymmetrically in most cases.

The connective tissue capsule covering each of them from the outside has processes directed inside the thickness of the glandular tissue, which divide the organ into lobules, and are rather weakly expressed.

The parathyroid gland is a parenchymal organ with a trabecular structure. The parenchyma is represented by epithelial cells that form cords, and the space between them is filled with connective tissue, generously supplied with a network of blood vessels, as well as accumulations of fat.

Structural elements of the gland

Individual trabeculae are built from two types of parathyroid cells - active cells of the parathyroid glands:

Basophilic or major.
Oxyphilic.

In turn, the main parathyroid cells are divided into two more types, differing in their functional state:

Dark (active).
Light (low-active).

The main active components of the parathyroid glands are dark basophilic parathyroid cells. They actively function, providing the functions of the parathyroid gland, due to the presence of more developed Golgi complexes and granular endoplasmic reticulum.

In the cytoplasm of dark basophilic cells there are many secretory granules, the diameter of which is no more than 400 nm; parathyrin, the hormone of this endocrine organ, is deposited in them. The parathyroid gland uses it to regulate the content of calcium ions in the blood.

In this case, the secretion of biologically active substances is carried out on the basis of the feedback principle - as soon as the calcium content in the peripheral blood drops, the production of parathyrin increases and, conversely, when the concentration of this microelement begins to exceed the norm, the iron reduces the secretion of the hormone.

Parathyroid hormone

Parathyroid hormone is the only biologically active substance that is synthesized by the secretory cells of the parathyroid glands. Its main function is to maintain a stable level of ionized calcium in the blood.

Calcium is the main microelement that represents the internal structure of bone tissue. It is responsible for strong and healthy bones, normal functioning of the heart and muscle tissue.

This is interesting. In total, the body contains about 1000 g of calcium, and 99% of it is contained in hydroxyapatite in long tubular and flat bones.

The release of parathyroid hormone by the secretory cells of the parathyroid glands is triggered by a decrease in blood calcium levels.

Normal values for this microelement:

2.250-2.750 mmol/l;
or 9-11 mg/100 ml.

Parathyroid hormone stimulates the activity of osteoclasts - cells that destroy bone tissue, thereby provoking a massive release of calcium into the blood and restoration of homeostasis. Like any other hormonal substance, parathyroid hormone acts by a feedback mechanism: restoration of normal calcium concentration leads to a decrease in its production. Thus, parathyroid hormones are an antagonist of calcitonin produced by the C-cells of the thyroid gland.

Table: Comparison of parathyroid hormone and calcitonin:

In addition to demineralizing bone tissue, parathyroid hormone increases calcium levels in the body by:

increasing the reabsorption of the microelement in the kidney tubules - reducing its excretion in the urine;
Increased synthesis of vitamin D, which enhances calcium absorption in the intestine.

Biological role of the parathyroid glands in the body

Thus, the parathyroid glands are responsible for maintaining a stable level of calcium in the blood and maintaining a constant internal environment. Calcium is a trace element that is necessary for the normal functioning of most internal organs.

Effect of the parathyroid glands on muscles

Active muscle contractions are possible only with the participation of calcium, the ions of which transfer nerve cells from one myocyte to another, “forcing” the muscle to work. Calcium deficiency, caused by a decrease in the production of parathyroid hormone, can lead to muscle weakness, general fatigue, myalgia, and poorly controlled cramps.

Effect of the parathyroid glands on the heart

The heart is the largest muscle in the human body and consumes large amounts of energy every day. Calcium is also necessary for its normal operation and timely transmission of excitation from the autonomous node to cardiomyocytes. A lack of microelement provokes the development of arrhythmias of various types.

Effect of the parathyroid glands on the nervous system

A sufficient level of calcium is also required for the rapid transmission of impulses through the neurons of the brain. The parathyroid glands indirectly influence the activity of mental activity.

The influence of the parathyroid glands on the lens of the eye

Parathyroid hormone helps reduce calcium deposits in the lens tissue, so when the parathyroid glands are insufficient, a person often develops cataracts.

The influence of the parathyroid glands on the blood

Calcium ions are also required for the normal functioning of the blood coagulation system. Rapid stoppage of bleeding during injury is another important function of the homeostasis system in which the parathyroid glands participate.

Endocrine disorders associated with dysfunction of the parathyroid glands

Diagnostics

The functions of the parathyroid gland can be studied in various ways. The most common methods, the price of which is quite affordable, include a blood test for parathyroid hormone, ultrasound, urine tests to determine calcium levels, as well as radiography and scintigraphy.

Somewhat less frequently, CT, MRI or histological examination are used. Instructions for conducting histology involve collecting material and assessing the functional state of cells and tissues.

Parathyroid gland - histology is performed to identify formations or after surgical interventions. The analysis determines that each of the glands is covered with a connective fibrous capsule.

Layers consisting of loose connective tissue extend from the capsules. These layers form the stroma of the glands and are streaked with multiple blood vessels, with a predominance of capillaries.

The cells underlying the glandular epithelium - parathyrocytes - tend to form groups and cords that lie between the layers of connective tissue and are in contact with hemocapillaries.

When a site producing hormones with pathological activity appears in one of the parathyroid glands, they speak of the development of hyperparathyroidism.

This pathology, in turn, provokes the development of:

hypercalcemia;
parathyroid osteodystrophy.

These diseases can occur due to the following factors:

parathyroid adenomas;
hormonally active parathyroid cancer;
diffuse enlargement of the parathyroid glands;
malabsorption syndrome;
chronic renal failure;
injuries and hemorrhages in the pancreatic gland;
vitamin D deficiency;
liver cirrhosis;
inflammatory processes in the parathyroid glands;
metastases to the glands and neck area;
congenital underdevelopment of glands;
autoimmune and systemic diseases;
surgical operations with damage to the parathyroid glands;
endocrine pathologies.

Primary and secondary insufficiency of the parathyroid glands is called hypoparathyroidism.

Parathyroid disease is diagnosed based on a typical clinical picture, laboratory testing of parathyroid hormone levels (average price in private laboratories - 600 rubles), and ultrasound. Before treatment, you need to consult a doctor - you cannot cure hormonal imbalance with your own hands. Medical instructions involve creating an individual treatment plan for each specific patient.

Note! Congenital underdevelopment of the parathyroid glands leads to severe disturbances in phosphorus-calcium metabolism and is diagnosed during the neonatal period. Such patients require lifelong parathyroid hormone replacement therapy. Removal of all parathyroid glands in animals led to rapid death, which was preceded by a period of short-term muscle cramps.

Now that we are familiar with the biological role of these small but very important endocrine organs, you can easily list the functions of the parathyroid glands and the effect they have on the body. Violation of parathyroid hormone secretion is quite rare, but in any case requires timely diagnosis and treatment.