Case Report: Three Patients With Substantial Serum Levels of 3-Epi-25(OH)D Including One With 3-Epi-25(OH)D2 While on High-Dose Ergocalciferol

Context: We report the presence of substantial concentrations of 3-epi-25(OH)D-3 in two patients and a third patient with 3-epi-25(OH)D-2. Patients: The first patient, a 66-year-old female receiving cholecalciferol 4000 IU daily was originally found to have 53 ng/mL of 25(OH)D-3 and almost an equal amount of 3-epi-25(OH)D-3. Subsequently, the patient had four additional samples, each of which has similar levels of both 25(OH)D-3 and 3-epi-25(OH)D-3. The second patient, a 7-year-old male receiving cholecalciferol 1000 IU daily, hada 25(OH)D-3 concentration of 37ng/mL and 3-epi-25(OH)D-3 of approximately 10 ng/mL. The third and most intriguing patient, a 55-year-old female was receiving ergocalciferol 50 000 IU twice weekly for approximately 3 months, at which time her serum 25(OH)D-2 was 64 ng/mL and her 3-epi-25(OH)D-2 was approximately 32 ng/mL. This patient's physician changed her vitamin D therapy to cholecalciferol 1000 IU daily, discontinuing ergocalciferol, and a second specimen was collected 5 months later. Analysis of this last specimen found both 25(OH)D-3 and 25(OH)D-2 at concentrations of 12 and 24 ng/mL respectively, plus corresponding 3-epimer peaks for both 25(OH)D-3 and 25(OH)D-2 observed chromatographically. Conclusion: The presence of a substantial concentration of 3-epi-25(OH)D in these three patients documents that one cannot assume 3-epi is a trivial metabolite of 25(OH)D for all patients. In addition, the appearance of 3-epi-25(OH)D-3 when the last patient changed her vitamin D supplementation from ergocalciferol to cholecalciferol demonstrates that the 3-epimer is probably an endogenous metabolite of 25(OH)D in humans.