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Background: Sporadic multiple parathyroid gland disease is ¼ cases of primary hyperparathyroidism (PHPT). However, a single tactic for diagnosing and operating volume in patients with this variant of PHPT has not yet been developed. One of the possible directions in the search for pathogenetically substantiated methods of diagnosis and treatment is the study of the molecular genetic features of the disease and associated clinical and laboratory factors., Aim: To study the features of the expression of calcium sensitive (CaSR) and vitamin D (VDR) receptors on the surface of parathyroid cells in primary hyperparathyroidism with solitary and multiple lesions of the parathyroid glands, as well as its changes under the influence of a decrease in the filtration function of the kidneys., Materials and Methods: In a single center observational prospective study with retrospective data collection, there were patients who during 2019-2021. operated on for PHPT, secondary hyperparathyroidism (SHPT) and all cases of tertiary hyperparathyroidism (THPT) operated during 2014-2021. The expression of CaSR, VDR and its relationship with the main laboratory parameters, the clinical variant of hyperparathyroidism, and the morphological substrate were studied., Results: The study included 69 patients: 19 with multiple and 25 with solitary PTG near PHPT, 15 with SHPT, 10 with THPT. A statistically significant decrease in the frequency of detection of normal expression of CaSR and VDR receptors occurs in any morphological variant of hyperparathyroidism and is observed in 93-60% of drugs. A decrease in the normal expression of CaSR in hyperplasia is detected statistically significantly less frequently than in adenoma (p≤0.01). The median expression intensity in adenoma was 2.5 (2:3), in hyperplasia 3.5 (3-4) (p≤0.01). The difference in the molecular mechanisms of the development of hyperparathyroidism with a predominance of a morphological substrate in the form of adenoma (PHPT with solitary adenoma) or hyperplasia (SHPT and PHPT with multiple PTG lesions) is realized in the frequency of maintaining normal CaSR expression in the PTG tissue. These mechanisms are implemented at the local level, their variability does not change under the influence of RRT. A common molecular genetic mechanism for the development of hyperparathyroidism with a predominance of a morphological substrate in the form of adenoma or hyperplasia has been found to reduce the frequency of maintaining normal VDR expression in PTG (up to 7-13%), p<0.01. This mechanism is implemented at the local level, its variability changes under the influence of RRT, reaching statistically significant differences in patients with THPT., Conclusion: The study demonstrates the features of changes in the expression of CaSR and VDR in PHPT with multiple lesions of the parathyroid glands. The relationship between the expression of these receptors and the clinical variant of hyperparathyroidism, the morphological substrate, the main laboratory parameters, and renal function was shown.

This comprehensive experimental study had the objective to determine the optimum ratio of calcium and vitamin D used as additives in food compositions and provide an experimentally-based rationale for the use of new functional dairy products and evaluation of their nutritional value. Experimental medico-biological assessment was conducted using growing male Wistar rats by balance and biochemical methods. It was shown that the calcium/vitamin D ratio in foodstuffs determines their functional efficiency. High nutritive and biological value was documented for some new cottage cheese products rich in calcium (240 mg%) and vitamin D (1 mg%). Results of the study were used to develop guidelines for the enrichment of various food compositions with calcium and vitamin D and substantiate methods for the assessment of their real functional effectiveness.

The authors studied influence of calcium included into ratio on rat's antioxidant system functioning in experimental activation of lipids peroxidation. The results prove decompensation of enzymatic and non-enzymatic units of antioxidant system, both with normal and deficient calcium. At the same time, higher calcium intake resulted in adequate cellular adaptation to peroxidation.

Chronic intake of Sr for 20 days by chickens caused in them a delay in body mass increase and symptoms of rickets in spite of complete provision with vitamin D. There were low levels of Ca, P, enhanced activity of alkaline phosphatase in the serum, inhibited mineralization of bone tissue, reduced levels of vitamin D-dependent calcium-binding protein, Sr accumulation in various tissues. Enrichment with Ca of the chickens ration diminished the above signs of Sr toxicosis. It is suggested that a protective effect of Ca in chronic Sr toxicity may be due to more active discrimination of Sr against Ca in intestinal assimilation of these cations.

The replacement of 1/5 part of the usual ration received by non-inbred white rats for fish mass containing up to 4 g/kg Ca resulted in a sharp (by 70%) reduction of Sr-90 accumulation after its oral intake. The effect is intensified in case of normalization of the basic ration in respect to Ca content, and the lowering of the isotope accumulation level in the skeleton comprises 82% as compared to the group of animals that received the Ca-deficient ration.

The content of organic mineral components in bones was studied after substitution of 25 and 50% of carbohydrate energy value in rations for saccharose. It was established that saccharose stimulated the growth of experimental animals, this was attended by increased phosphomonoesterase-1 activity, epiphyseal cartilage thickening, hyperfunction of the growth zone and changes in the phosphorus-calcium metabolism.

Electrolytic imbalance is a frequent finding in malabsorption syndrome. Derangement of calcium metabolism present clinically in different variants is most serious. Some patients develop hypocalcemia manifesting clinically with specific myasthenia, paresthesias, convulsions, hemorrhages, etc. In other variants severe skeletal lesions are seen which may become dominating in the clinical picture though hypocalcemia was absent. Investigation of calcium metabolism, hormonal profile (parathormone, in particular) in malabsorption syndrome can prognosticate and prevent the onset of osteomalacia.

Alimentary osteopathies are classified into primary (with food deficient of Ca, vitamin "D", or of proteins) and secondary ones, that develop consequent to disturbed assimilation and absorption of these substances. Basic causes responsible for the development of alimentary osteopathies are listed and the pathogenesis of this malady is considered. The osteopathies are classified with respect to their causes, the prevalent form (osteoporosis, osteomalacia, or mixed forms) and according to the severity of the skeletal affection (latent stage, that of clinical manifestation and the stage with complications). A review of modern methods of diagnosis and therapy in dealing with alimentary osteopathies by using calcium, vitamin "D" and fluorine, as well as by applying other remedies (thyrocalcitonin, estrogens, androgens, anabolic hormones, diphosphonates) or measures (exercises, rehabilitation) is presented.

In 12 patients with jaw-bones fractures an investigation of calcium and magnesium metabolism was carried out with a view of elucidating its possible relation to the course of repair of the bone tissue. A reciprocal dependence in the calcium and magnesium ions exchange in lesions of the jaws and an intensified accumulation of these ions by the time of the initial formation of the secondary callus were revealed. Investigations have confirmed the important role of magnesium in the metabolism of the bone tissue and a study of two diets with different magnesium content justified recommending its daiy allowance of about 550 mg for the given patients' population.

Keeping rats on a ration with a 1:3 proportion of calcium and phosphorus for 2 weeks results in hyperprosphatemia, hypocalcemia and renal calcinosis with uremia. When putting these animals on a food ration with the calcium and phosphorus ratio of 1:1 the concentration of these elements in the blood quickly returns back to normal, while renal calcinosis continues for the whole period of observation (7 months). The growing animals are more sensitive to a phosphorus excess than are the adult ones. An excessive consumption of phosphorus leads to its increased excretion with the urine with concurrent diminution of the calcium excretion. The blood and urine pH then experiences no change, whereas the ability of the turned inside out segments of the small intestine to absorb calcium as against the concentration gradient (active transport) in vitro not only does not diminish, but initially even goes up. It is suggested that the excess phosphorus content in the food ration tends to directly derange absorption of calcium in the intestines, this resulting in the development of hypocalciemia, hyperparathyroidism and calcinosis of the viscera and tissues.