BACKGROUND:Vitamin D (25-hydroxyvitamin D [25(ОН)D]) deficiency (<20 ng/mL) and insufficiency (20-29 ng/mL) are common in primary hyperparathyroidism (PHPT), but data regarding the vitamin D metabolism in this population is limited.AIM:The aim of this study is to estimate the vitamin D metabolites and their relationship with the main parameters of phosphorus-calcium metabolism in patients with PHPT at baseline and on the background of a single dose of cholecalciferol 150,000 IU.MATERIALS AND METHODS:A single-center interventional, dynamic, prospective, comparative study has been carried out. The study included 54 participants, divided into two groups: the 1st group included 27 patients with confirmed PHPT, the 2nd control group (n = 27), matched on gender (p = 0.062). The study included 4 visits; the baseline laboratory examination and a bolus dose of cholecalciferol were performed at the visit 1, the subsequent visits included a dynamic laboratory examination.RESULTS:Vitamin D deficiency (<20 ng/ml) was detected in 69% of patients with PHPT. In the PHPT group (before cholecalciferol therapy), there was a direct association of 1.25(OH)2 D3 with albumin-corrected and ionized calcium, as well as between the 25(OH)D3 /24.25(OH)2 D3 ratio with PTH and magnesium. After taking of cholecalciferol, the levels of 1.25(OH)2 D3 and 25(OH)D3 /24.25(OH)2 D3 were significantly increased, and the levels of 25(OH)D3 /1.25(OH)2 D3 were significantly declined at all visits among patients with PHPT. The common 25(OH)D level was comparable to the control group, however the levels of 1,25(OH)2 D3 in patients with PHPT were 55% higher at baseline, and after taking of cholecalciferol 150,000 IU. They remained increased by 3-7 days by an additional 23-36%, significantly higher than those in the control group: 44%, 74% and 65%, at visits 2, 3 and 4, respectively (p<0.05). The taking of 150,000 IU cholecalciferol in the PHPT group did not lead to a significant increase in hypercalcemia and hypercalciuria, which indicates the safety of this dose in patients with mild hypercalcemia (albumin corrected calcium <3 mmol/l). None of the study participants experienced any side effects.CONCLUSION:The completely comprehensive assessment of vitamin D metabolites was carried out for the first time in patients with PHPT before and after using a bolus dose of cholecalciferol. The results confirmed the differences of vitamin D metabolism in chronic excessive secretion of PTH compared to control group, which is new data in the pathogenesis of the disease, and can be used to develop optimal regimens for cholecalciferol taking in this population.

IV (XXVII) Национальный конгресс эндокринологов с международным участием «ИННОВАЦИОННЫЕ ТЕХНОЛОГИИ В ЭНДОКРИНОЛОГИИ» 22-25 сентября 2021 года НАРУШЕНИЕ МЕТАБОЛИЗМА ВИТАМИНА D У ГОСПИТАЛИЗИРОВАННЫХ ПАЦИЕНТОВ С COVID-19 Поваляева А .А ., Богданов В

Hypercalcemia associated with impaired vitamin D metabolism is a rare autosomal recessive disorder. The mechanism of this pathology is the impairment of inactivation of active metabolites of vitamin D because of mutations in the CYP24A1 gene, which leads to an increase of calcium absorption and the development of hypercalcemia, hypercalciuria, nephrocalcinosis and nephrolithiasis. The phenotype of the disease ranges from severe forms which are diagnosed in early infancy (severe hypercalcemia associated with dehydration, vomiting, nephrocalcinosis, and sometimes death) to milder forms, that often are diagnosed in adulthood and manifested with recurrent nephrolithiasis and nephrocalcinosis. Differential diagnosis is carried out with the most common causes of hypercalcemia: primary hyperparathyroidism and malignant neoplasms. To diagnose, the determination of vitamin D metabolites and genetic research are used. As a treatment for mild forms, it is recommended to limit dairy products, to keep a drinking regimen, to refuse taking vitamin D and calcium preparations, and use of sunscreens. The article presents a clinical case of parathyroid hormone-independent hypercalcemia due to mutation of the CYP24A1 gene of a 20-year-old patient suffering from nephrolithiasis and nephrocalcinosis since the age of 16 with a confirmed violation of vitamin D metabolism.