THU400 Parameters Of Vitamin D Metabolism, Calcium And Phosphate Homeostasis In Patients Undergoing Bariatric Surgery

Abstract Disclosure: A. Zhukov: Grant Recipient; Self; Russian Science Foundation (project 19-15-00243-P). A. Povaliaeva: Grant Recipient; Self; Russian Science Foundation (project 19-15-00243-P). Z. Abilov: Grant Recipient; Self; Russian Science Foundation (project 19-15-00243-P). L. Usoltseva: None. D. Trukhina: None. E. Pigarova: Grant Recipient; Self; Russian Science Foundation (project 19-15-00243-P). L. Rozhinskaya: Grant Recipient; Self; Russian Science Foundation (project 19-15-00243-P). Objective: to evaluate the parameters of vitamin D metabolism and calcium and phosphate homeostasis in patients undergoing bariatric surgery. Materials and Methods: The study included 10 patients without chronic kidney disease and mineral metabolism disorders who underwent laparoscopic gastric bypass surgery for obesity. After surgery, all patients were recommended to take cholecalciferol depending on the initial level of 25-OH D in blood in accordance with the Endocrine Society Clinical Practice Guideline. Ninety nine [96; 130] days after the surgery, the levels of vitamin D metabolites: D3, 25-OH D3, 24,25-OH2 D3, 1,25-OH2 D3 were determined by ultra-high performance liquid chromatography in combination with tandem mass spectrometry (certified by DEQAS) as well as the PTH, total calcium, albumin, creatinine, phosphorus, magnesium levels in serum. Results: Median age of the patients was 39 [34; 50] years, 80% women, 90% initially had type 2 diabetes mellitus (BMI before surgery 49.1 [39.7; 51.0] kg/m2, median decrease in BMI by the time of inclusion in the study 8.3 [8.0; 9.2] kg/m2). The median level of 25-OH D3 was 28.5 [24.6; 32.0] ng/ml (1 patient had a level less than 20 ng/ml, 6 patients from 20 to 30 ng/ml), D3 levels were below the laboratory sensitivity threshold (12.5 ng/ml) in all participants. The median 24,25-OH2 D3 level was 1.49 [1.04; 1.95] ng/ml (reference interval (RI) 0.5-5.6 ng/ml), the median 25-OH D3/24,25-OH2 D3 ratio was 21.87 [15.57; 22.55] (RI 7-23). All patients had normal levels of 1,25-OH2 D3 (median 45.95 [35.18; 53.65] pg/ml, RI 25-66). One patient had secondary hyperparathyroidism (albumin-adjusted calcium 2.14 mmol/l, RI 2.15-2.55; PTH 73.8 pg/ml, RI 15-65; 25-OH D3 24.8 ng/ml) while other biochemical parameters were normal. The remaining patients had normal levels of PTH, calcium, phosphorus and magnesium. Conclusions: The revealed changes in the levels of D3 and 25-OH D3 in patients undergoing bariatric surgery may be due to malabsorption, increased deposition in adipose tissue, an insufficient dosage of cholecalciferol or low patient compliance. At the subsequent stages of vitamin D metabolism, no abnormalities were identified. It is likely that this cohort of patients requires higher doses of cholecalciferol. Presentation: Thursday, June 15, 2023