Prevalence of hypercalcemia related to hypervitaminosis D in clinical practice

Summary Background and aim Recent interest in vitamin D has led to a substantial increase in the use of vitamin D supplements. Vitamin D intoxication may be a concern as hypervitaminosis D can result in irreversible calcification of soft tissues so that it is important to detect early markers of vitamin D intoxication. Our aim was to assess the simultaneous presence of biochemical markers of vitamin D toxicity (i.e. hypervitaminosis D, hypercalcemia) and determine the concentrations of 25-OH-vitamin D at which the risk of hypercalcemia, and thus toxicity, might begin. Methods We evaluated retrospectively a 6-year period during which 25.567 samples were assessed for 25-OH-vitamin D status by UHPLC. Hypervitaminosis D was defined at serum 25-OH-vitamin D >160nmol/L. Serum and urine calcium, phosphorus and iPTH were also recorded, if available. Medical history revision was performed in subjects displaying simultaneously hypervitaminosis D and hypercalcemia. Results Overall, hypervitaminosis D was found in 475 samples (1.86%) of which 51 displayed hypercalcemia (11.1%). A total of 382 samples were identified as the first record of hypervitaminosis D and 39 presented hypercalcemia (10.2%), most of them at 25-OH-vitamin D levels between 161-375 nmol/L. Only in 15 subjects, hypercalcemia could be directly attributed to vitamin D and serum 25-OH-vitamin D ranged between 164-1139 nmol/l. In no case, serum calcium achieved concentrations considered as critical values (>13 mg/dl). Conclusion Hypercalcemia due to vitamin D represented < 4% of the total hypervitaminosis D detected and