ODP096 Hypercalcemia Secondary to Vitamin D Supplementation with Normal 25-Hydroxyvitamin D Level in an Elderly Female - Case Report

CASE PRESENTATION: A 92-year-old female with a history of heart failure, dementia (alert and oriented to time, place and person at baseline), osteoporosis and hypothyroidism presented to the emergency department with altered mental status and constipation. She was oriented to time and person only. Labs included: WBC count 6.2 (4 - 11k/mm cu), Creatinine 1.23 (0.6 - 1.2 mg/dL), Calcium 12.8 (8.6 - 10.3 mg/dL), Albumin 3.9 (3.5 - 5.7 g/dL) and Glucose 94 (70 - 99 mg/dL). CT head showed no acute abnormality. Medication reconciliation revealed that she was taking Cholecalciferol (Vitamin D3) 2000 units daily, which was held. Intravenous fluids were started and further workup was done: PTH < 6 (12 - 88 pg/mL), serum 25 Hydroxyvitamin D 45.1 (30 - 100 ng/mL), serum 1, 25 Dihydroxyvitamin D 79 (19.9 - 79.3 pg/ml) and PTHrP 2.6 (0 - 3.4 pmol/L). Endocrinology was consulted for management of PTH independent hypercalcemia and recommended Zoledronic acid. Serum calcium levels normalized with bisphosphonate therapy and withholding of Vitamin D3 supplementation in addition to symptomatic improvement. Repeat 1-25-Dihydroxyvitamin D level decreased to 38.3 pg/mL while repeat PTH normalized at 20.8 pg/mL. Subsequently, serum calcium levels remained within normal limits, and she was discharged. DISCUSSION: Vitamin D, the "sunshine Vitamin", has claimed much fame and popularity for its varied benefits. With a growing user base, there is concern for potential adverse effects, primarily involving the population with an underlying propensity for hypercalcemia. According to the NIH, the safe upper limit of daily Vitamin D intake is 4000 IU; however, for adults > 70 years of age, 800 IU is the recommended dose. Our patient was taking 2000 IU (almost 2.5 times the recommended dose) of Vitamin D3, the most potent form which raises Vitamin D levels twice as fast as Vitamin D2. In addition, her serum 1,25 Dihydroxyvitamin D levels normalized when supplementation was withheld pointing to a cause - effect relationship and thus, effectively ruling out an endogenous source. Moreover, other factors such as prolonged duration of supplement intake, advanced age, immobility, osteoporosis and hypothyroidism contributed to her hypercalcemia. Current review of literature suggests that serum concentrations of 25-Hydroxyvitamin D at which hypercalcemia arises remains undefined. With this case, we wish to emphasize that a holistic approach should be utilized to advise patients regarding Vitamin D supplementation considering pre-existing risk factors for hypercalcemia, concurrent medical conditions, diet and functional status. Although current guidelines detail the ideal dosage and duration of Vitamin D supplementation therapy for different sectors of population, streamlining and individualizing therapy to mitigate potential harm to patients is pivotal. Presentation: No date and time listed