Objective: Calcitriol excess is a less common cause of hypercalcemia than hyperparathyroidism. Hypercalcemia due to calcitriol excess is usually managed acutely with intravenous (IV) fluid administration and dietary calcium restriction. Steroids and ketoconazole are second-line agents. There is evidence supporting the role of bone resorption in the genesis of hypercalcemia in vitamin D intoxication and for a rapid response of hypercalcemia to treatment with bisphosphonates. We seek to demonstrate the utility of bisphosphonates in calcitriol-induced hypercalcemia (CIH).
Methods: We present the case of a patient with recurrent CIH from a follicular lymphoma who achieved normalization and subsequent stabilization of serum calcium levels following bisphosphonate administration.
Results: A 77-year-old woman with a history of non-small cell lung cancer was admitted with dry mouth, polyuria, weight loss, and fatigue. She was found to have a calcium level of 14.7 mg/dL (normal range is 8.5 to 10.2 mg/dL), 25-hydroxyvitamin D of 47 ng/mL (normal range is 30 to 60 ng/mL), 1,25-dihydroxyvitamin D of 89 pg/mL (normal range is 18 to 72 pg/mL), and parathyroid hormone of 19 pg/mL (normal range is 15 to 65 pg/mL), which recurred despite treatment with IV fluids and strict low-calcium diet. She received 5 mg of IV zoledronic acid and normocalcemia was maintained thereafter, without any diagnosis-specific treatment for >3 months. Positron emission tomography with computed tomography eventually showed new innumerable foci of increased uptake in the skeleton and lymph node biopsy revealed grade 3A follicular lymphoma.
Conclusion: The first choice for CIH is treating the underlying cause. Bisphosphonates are, however, useful until a diagnosis is made, as they may be safer than steroids and can provide rapid relief even with a single treatment with minimal side effects.
Copyright © 2019 AACE.