Diseases associated with changes in phosphorus-calcium metabolism occur in people of both sexes, regardless of age. Phosphorus and calcium are vital, indispensable chemicals for the full he alth of a person. Surely each of us knows that bone tissue contains more than 90% of calcium and about 80% of phosphorus reserves from the whole body. In small quantities, these components are present in ionized blood plasma, nucleic acids and phospholipids.
Calcium and phosphorus metabolism in early life
During the first year of life, the risk of metabolic disorders is the highest, which is associated with the rapid growth and development of the baby. Normally, a child triples the body weight given from birth in the first 12 months, and from 50 average centimeters at birth, a one-year-old toddler grows to 75. In children, phosphorus-calcium metabolismmanifested by a relative or absolute deficiency of useful minerals and substances in the body.
Many factors lead to these problems:
- vitamin D deficiency;
- violation of his metabolism due to the immaturity of enzyme systems;
- impaired intestinal absorption and renal reabsorption of phosphorus and calcium;
- diseases of the endocrine system.
Much less commonly diagnosed are hypercalcemic conditions, which are an excess of calcium and phosphorus. An excessive amount of chemicals in the body is no less dangerous for the he alth of the child and requires medical correction. However, to achieve such a state with a normal diet is almost impossible. So the daily need for calcium in infants is equal to 50 mg per 1 kg of body weight. Therefore, a child who weighs about 10 kg should receive about 500 mg of Ca daily. 100 ml of mother's milk, which is the only source of nutrients, contains about 30 ml of Ca, and cow's milk contains more than 100 mg.
Biochemistry of phosphorus-calcium metabolism
After these chemicals enter the body, they are absorbed in the intestines, then they are exchanged between blood and bone tissue, followed by the release of calcium and phosphorus from the body with urine. This stage is called reabsorption, which takes place in the renal tubules.
The main indicator of a successful Ca exchange is its concentration in the blood, which normally varies within2, 3–2, 8 mmol/l. The optimal content of phosphorus in the blood is considered to be 1.3-2.3 mmol / l. Important regulators of calcium-phosphorus metabolism are vitamin D, parathyroid hormone and calcitonin produced by the thyroid gland.
Half of the calcium contained in the blood has a direct relationship with plasma proteins, in particular albumin. The rest is ionized calcium, which seeps through the capillary walls into the lymphatic fluid. Ionized calcium serves as a regulator of many intracellular processes, including the transmission of impulses through the membrane into the cell. Thanks to this substance, a certain level of neuromuscular excitability is maintained in the body. Plasma protein-bound calcium is a kind of reserve to maintain a minimum level of ionized calcium.
The reason for the development of pathological processes
The predominant share of phosphorus and calcium is concentrated in inorganic s alts of bone tissue. Throughout life, hard tissues form and break down due to the interaction of several types of cells:
- osteoblasts;
- osteocytes;
- osteoclasts.
Bone tissue is actively involved in the regulation of phosphorus-calcium metabolism. The biochemistry of this process guarantees the maintenance of a stable level in the blood. As soon as the concentration of these substances drops, which becomes apparent in terms of 4.5-5.0 (it is calculated by the formula: Ca multiplied by P), the bone begins to rapidly collapse due to increased activityosteoclasts. If this indicator significantly exceeds the specified coefficient, s alts begin to be deposited in the bones in excess.
All factors that negatively affect the absorption of calcium in the intestine and impair its renal reabsorption are direct causes of hypocalcemia. Often in this condition, Ca is washed out of the bones into the bloodstream, which inevitably leads to osteoporosis. Excessive absorption of calcium in the intestine, on the contrary, entails the development of hypercalcemia. In this case, the pathophysiology of phosphorus-calcium metabolism is compensated by intense Ca deposition in the bones, and the rest leaves the body with urine.
If the body is unable to maintain a normal level of calcium, it is a natural consequence of diseases caused by a deficiency of a chemical element (as a rule, tetany is observed) or its excess, which is characterized by the development of toxicosis, Ca deposition on the walls of internal organs, cartilage.
The Role of Vitamin D
Ergocalciferol (D2) and cholecalciferol (D3) are involved in the regulation of phosphorus-calcium metabolism. The first type of substance is present in small quantities in oils of vegetable origin, wheat sprouts. Vitamin D3 is more popular - everyone knows about its role in the absorption of calcium. Cholecalciferol is found in fish oil (mainly salmon and cod), chicken eggs, dairy and sour-milk products. Daily human need for vitamin Dis approximately 400-500 IU. The need for these substances increases in women during pregnancy and lactation, so it can reach 800-1000 IU.
Full intake of cholecalciferol can be ensured not only by the consumption of these foods or vitamin supplements to food. Vitamin D is formed in the skin under the influence of UV rays. With a minimum duration of insolation in the epidermis, the amount of vitamin D necessary for the body is synthesized. According to some reports, ten minutes of exposure to the sun with open hands is enough.
The reason for the lack of natural ultraviolet insolation are, as a rule, meteorological and geographical conditions of the area of residence, as well as domestic factors. You can compensate for the lack of vitamin D by eating foods with a high content of cholecalciferol or taking medications. In pregnant women, this substance accumulates in the placenta, which guarantees the protection of the newborn from rickets during the first months of life.
Since the main physiological purpose of vitamin D is to participate in the biochemistry of phosphorus-calcium metabolism, its role in ensuring the full absorption of calcium by the intestinal walls, the deposition of trace element s alts in bone tissues, and the reabsorption of phosphorus in the renal tubules cannot be ruled out.
In conditions of calcium deficiency, cholecalciferol starts the processes of bone demineralization, enhances the absorption of Ca, thereby trying to increase its level in the blood. Once the concentrationtrace element reaches the norm, osteoblasts begin to act, which reduce bone resorption and prevent its cortical porosity.
Scientists were able to prove that the cells of internal organs are sensitive to calcitriol, which is involved in the systemic regulation of enzyme systems. The launch of the corresponding receptors through adenylate cyclase causes the interaction of calcitriol with the calmodulin protein and enhances the transmission of impulses to the entire internal organ. This connection produces an immunomodulatory effect, regulates pituitary hormones, and also indirectly affects the production of insulin by the pancreas.
Involvement of parathyroid hormone in metabolic processes
An equally significant regulator is parathyroid hormone. This substance is produced by the parathyroid glands. The amount of parathyroid hormone, which regulates phosphorus-calcium metabolism, increases in the blood with a lack of Ca intake, leading to a decrease in the plasma content of ionized calcium. In this case, hypocalcemia becomes an indirect cause of damage to the kidneys, bones and digestive system.
Parathyroid hormone provokes an increase in calcium and magnesium reabsorption. At the same time, phosphorus reabsorption is markedly reduced, which leads to hypophosphatemia. In the course of laboratory studies, it was possible to prove that parathyroid hormone increases the likelihood of calcitriol entering the kidneys and, as a result, increasing intestinal absorption of calcium.
Present in bone tissue under the influenceparathyroid hormone calcium changes its solid form to a soluble one, due to which the chemical element is mobilized and released into the blood. The pathophysiology of calcium-phosphorus metabolism explains the development of osteoporosis.
Thus, parathyroid hormone helps to save the right amount of calcium in the body, participating in the homeostasis of this substance. At the same time, vitamin D and its metabolites are endowed with the function of constant regulation of phosphorus and calcium in the body. Parathyroid hormone production is stimulated by low blood calcium levels.
What is calcitonin used for
Phosphorus-calcium metabolism needs a third indispensable participant - calcitonin. It is also a hormonal substance produced by the C-cells of the thyroid gland. Calcitonin acts as a parathyroid hormone antagonist on calcium homeostasis. The rate of hormone production increases with an increased concentration of phosphorus and calcium in the blood and decreases with a lack of intake of the corresponding substances.
You can provoke active secretion of calcitonin with the help of a diet enriched with calcium-containing foods. This effect is neutralized by glucagon, a natural stimulator of calcitonin production. The latter protects the body from hypercalcemic conditions, minimizes the activity of osteoclasts and prevents bone resorption by intensive accumulation of Ca in bone tissue. "Extra" calcium, thanks to calcitonin, is excreted from the body with urine. The possibility of an inhibitory effect of the steroid on the formation of calcitriol in the kidneys is assumed.
In addition to parathyroid hormone, vitamin D and calcitonin, other factors can also influence phosphorus-calcium metabolism. So, for example, microelements such as magnesium, aluminum, strong, can prevent the absorption of Ca in the intestine, replacing the calcium s alts of bone tissue. With prolonged treatment with glucocorticoids, osteoporosis develops, and calcium is washed into the blood. In the process of absorption in the intestines of vitamin A and vitamin D, the former has an advantage, therefore, it is necessary to consume foods containing these substances at different times.
Hypercalcemia: Consequences
The most common disorder of phosphorus-calcium metabolism is hypercalcemia. Increased serum Ca content (more than 2.5 mmol/l) is a characteristic feature of hypersecretion of the parathyroid glands and hypervitaminosis D. In the analysis of phosphorus-calcium metabolism, an increased calcium content may indicate the presence of a malignant tumor in the body or Itsenko-Cushing's syndrome.
A high concentration of this chemical element is characteristic of patients with peptic ulcer of the gastrointestinal tract. Often the cause is excessive consumption of dairy products. Hypercalcemia is an ideal condition for the formation of stones in the kidneys. Phosphorus-calcium metabolism affects the functioning of the entire urinary system, lowers neuromuscular conduction. In severe cases, the possibility of developing paresis and paralysis is not excluded.
In a child, prolonged hypercalcemia may result in a delay ingrowth, regular stool disorders, constant thirst, muscle hypotension. With violations of phosphorus-calcium metabolism in children, arterial hypertension develops, the central nervous system is affected, which is expressed by confusion, memory lapses.
What threatens calcium deficiency
Hypocalcemia is diagnosed much more frequently than hypercalcemia. In most cases, it turns out that the reason for the lack of calcium in the body is the hypofunction of the parathyroid glands, the active production of calcitonin and poor absorption of the substance in the intestine. Calcium deficiency often develops in the postoperative period as a response of the body to the introduction of an impressive dose of an alkaline solution.
In patients with disorders of phosphorus-calcium metabolism, the symptoms are as follows:
- there is an increased excitability of the nervous system;
- tetany develops (painful muscle contractions);
- the feeling of "goosebumps" on the skin becomes permanent;
- possible seizures and respiratory problems.
Features of the course of osteoporosis
This is the most common consequence of disorders associated with phosphorus-calcium metabolism in the body. This pathological condition is characterized by low bone mass and a change in the structure of bone tissue, which leads to an increase in its fragility and fragility, and hence an increase in the risk of fracture. Doctors almost unanimously agree that osteoporosis is a disease of modern man. The risk of developing osteoporosis is especially high in the elderly, but withThe negative impact of technological progress, reduced physical activity and exposure to a number of adverse environmental factors increases the proportion of patients of mature age.
Each year, 15-20 million people are diagnosed with osteoporosis. The overwhelming majority of patients are women in menopause, as well as young women after removal of the ovaries, uterus. Approximately 2 million fractures each year are associated with osteoporosis. These are fractures of the femoral neck, spine, bones of the limbs and other parts of the skeleton.
If we take into account the information from WHO, then the pathology of the skeleton and bone tissue in terms of prevalence among the population of the Earth is second only to cardiovascular, cancerous diseases and diabetes mellitus. Osteoporosis can affect various parts of the skeleton, so any bone can be fractured, especially if the disease is accompanied by significant loss of body weight.
Metabolic diseases of the skeleton, in particular osteoporosis, are characterized by a significant decrease in the concentration of trace elements, in which the bone is resorbed much faster than it is formed. Thus, bone mass is lost and the risk of fracture increases.
Rickets in children
This ailment is a direct consequence of failures in phosphorus-calcium metabolism. Rickets develops, as a rule, in early childhood (up to three years) with a lack of vitamin D and disturbances in the absorption of trace elements in the small intestine and kidneys, which leads to a change in the proportion of calcium and phosphorus in the blood. It is worth noting that adults living in northern latitudes often experience problems with phosphorus-calcium metabolism due to a lack of ultraviolet radiation and a short stay in the fresh air during the year.
At the initial stage of the disease, hypocalcemia is diagnosed, which triggers the work of the parathyroid glands and causes parathyroid hormone hypersecretion. Further, as in a chain: osteoclasts are activated, the synthesis of the protein base of the bone is disrupted, mineral s alts are deposited in the missing amount, the leaching of calcium and phosphorus leads to hypercalcemia and hypophosphatemia. As a result, the child has a delay in physical development.
Characteristic manifestations of rickets are:
- anemia;
- irritability and irritability;
- cramps of the limbs and the development of muscle hypotonia;
- excessive sweating;
- disorders of the digestive system;
- frequent urination;
- X-shaped or O-shaped lower legs;
delayed teething and propensity for rapid progression of oral carious infection
How to treat such diseases
When metabolic disorders require complex complex treatment. Phosphorus-calcium metabolism, normalized, will eliminate most of the pathological consequences without any intervention. Therapy for osteoporosis, rickets and other metabolic disorders takes place in stages. Primarilyspecialists are trying to stop the resorption processes in order to prevent fractures, eliminate pain and return the patient to a working state.
Drugs for calcium-phosphorus metabolism are selected based on the symptoms of a secondary disease (most often osteoporosis, rickets) and the pathogenesis of bone resorption. Of no small importance for recovery is the observance of a diet built on the principle of a balance of proteins, calcium and phosphorus s alts. As auxiliary methods of therapy, patients are recommended massage, therapeutic exercises.
Drugs for the normalization of phosphorus-calcium metabolism
First of all, patients are prescribed drugs with a high content of vitamin D. These drugs are conditionally divided into two groups - drugs based on cholecalciferol and ergocalciferol.
The first substance stimulates intestinal absorption by improving the permeability of epithelial membranes. Basically, vitamin D3 is used to prevent and treat rickets in babies. Available in water-soluble ("Aquadetrim") and oil forms ("Vigantol", "Videin").
Ergocalciferol is absorbed in the intestines with active bile production, after which it binds to blood alpha globulins, accumulates in bone tissue, and remains as an inactive liver metabolite. Fish oil, which has been widely used in the recent past, is not recommended by pediatricians today. The reason for refusing to use this tool is the likelihood of side effects frompancreas, but despite this, pharmacies still offer fish oil in the form of dietary supplements.
In addition to vitamin D, in the treatment of disorders of phosphorus-calcium metabolism use:
- Calcium monopreparations containing the necessary chemical element in the form of s alts. Instead of the previously popular Calcium Gluconate, which is poorly absorbed in the intestines, Calcium Glycerophosphate, Calcium Lactate, and Calcium Chloride are now used.
- Combined drugs. Most often, complexes that combine calcium, vitamin D and other trace elements in their composition to facilitate the absorption of calcium ions (Natekal, Vitrum Calcium + Vitamin D3, Orthocalcium with magnesium, etc.
- Synthetic analogues of parathyroid hormone. Used by injection or as a nasal spray. In tablets, such drugs are not available, since when taken orally, the active substances are completely destroyed in the stomach. This group includes sprays "Miak altsik", "Vepren", "Osteover", powder "Calcitonin".
