Serum levels of 3-Epi-25-OH-D3 during Hypervitaminosis D in Clinical Practice

Context: Intoxication from vitamin D supplements has been rarely reported, but nowadays, it occurs more frequently. The presence of the C-3 epimer of 25-hydroxyvitamin D-3 (3-epi-25-OH-D-3) is highly prevalent in adults, although there is little information regarding its in vivo relevance, if any, especially under pathological conditions. Objective: Our aim was to assess the presence of the 3-epi-25-OH-D-3 in serum samples displaying 25-OH-D-3 concentrations indicative of hypervitaminosis D. Design, Setting, Patients, and Main Outcome Measure: A total of 58 samples displaying a wide range of concentrations of 25-OH-D-3 (>64-439 ng/ml) by ultrafast liquid chromatography were consecutively recruited and reassessed for the presence of 3-epi-25-OH-D-3 using a second chromatographic system. Data from additional biochemical tests performed as part of the patient evaluation were also recorded. Results: Mean relative contribution of 3-epi-25-OH-D-3 was less than 4%, and concentrations ranged from 2-28.6 ng/ml. Serum levels of the C3 epimer, but not the relative contribution, correlate with serum 25-OH-D-3. Overall, in subjects with 25-OH-D-3 concentrations indicative of hypervitaminosis D, the presence of the C-3 epimer and its levels were apparently unrelated to age, serum markers of renal and liver function, acute-phase reactants, and the presence of hypercalcemia. 3-Epi-25-OH-D-3 did not correlate with PTH, but subjects displaying PTH suppression (<14 pg/ml) showed higher concentrations of 3-epi-25-OH-D-3. Conclusion: The relative contribution of 3-epi-25-D-3 was not significantly altered during hypervitaminosis D, although the absolute levels reached in serum may be biologically relevant. From a clinical viewpoint, although the small size of the group may affect the lack of relationships, the presence of 3-epi-25-OH-D(3)s was apparently unrelated to serum markers of renal and liver function, acute-phase reactants, PTH, and the presence of hypercalcemia. (J Clin Endocrinol Metab 97: E2266-E2270, 2012)