MON-LB085 Blurred Vision and Hypocalcemia after Denosumab Injection in a Patient with Tertiary Hyperparathyroidism

Background: Denosumab is a human monoclonal antibody that targets the receptor activator of nuclear factor kappa B ligand (RANKL). It inhibits osteoclast-mediated bone resorption by binding to receptor. Denosumab prevents skeletal-related events (SREs) from osteoporosis and bone metastasis. However, there has been arising concern about hypocalcemia that is more vulnerable for patients with renal impairment due to elevated total osteoblast mass, coexisting calcitriol deficiency, inhibition by fibroblast growth factor 23. Clinical Case: A 66-year-old woman with ESRD on HD was transferred our endocrinology clinic for hypercalcemia and elevated intact parathyroid hormone(PTH); corrected calcium, 10.8 mg/dL(normal range: 8.5-10.2) and PTH, 164 pg/mL(8.00-72.00). I thought she had tertiary hyperparathyroidism(HPT). It is observed in patients with chronic secondary HPT who have been on dialysis therapy for years. I planned to examine sestamibi scan and neck ultrasonography to localize hypertrophied parathyroid glands. And then, I prescribed denosumab and a combined oral calcium/vitamin D supplement for her because she had persistent hypercalcemia and no medication for osteoporosis(DEXA T score is -3.8, -3.1 and -3.7 in L1-4, right femoral total, and neck respectively). After two weeks, she presented to our hospital for blurred vision of left eye. Papilledema and inferior visual field defect of left eye were observed in ophthalmology examination. Furthermore she had been receiving multiple dose of calcium and calcitriol injection during dialysis due to severe hypocalcemia at local dialysis center. Laboratory finding of dialysis clinic revealed corrected calcium decreased to 6.6 mg/dL(8.5-10.2) and PTH extremely increased to 3066 pg/mL(8.00-72.00). After rechecking her blood, laboratory work up showed corrected calcium, 7.7 mg/dL(8.5-10.2); 25(OH)vitamin D, 16.26 ng/mL(30-80); PTH, 1739 pg/mL(8.00-72.00). I examined sestamibi scan and neck USG. The results of sestamibi scan indicated hyperfunctioning parathyroid adenoma/hyperplasia in upper pole level of right thyroid gland and lower pole level of left thyroid gland that were matched with hypoechoic nodules of neck USG. We considered surgical interventions, total parathyroidectomy with autotransplantation or subtotal parathyroidectomy paying attention to postoperative complications such as hungry bone syndrome. Conclusion: Denosumab is an effective, tolerable anti-resorptive agent that has no nephrotoxicity, however, the risk of hypocalcemia is increasing, especially patients with chronic kidney disease. Hypocalcemia is a potentially life-threatening biochemical disorder that cause papilledema leading to the loss of vision. Therefore we should be aware of importance of monitoring calcium levels and renal function before and during denosumab therapy. Unless otherwise noted, all abstracts presented at ENDO are embargoed until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. Abstracts presented at a news conference are embargoed until the date and time of the news conference. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.