Effectiveness and safety of denosumab monotherapy in patients with primary hyperparathyroidism: A retrospective study

The appropriate treatment of osteoporosis and hypercalcemia using medications is important in patients with primary hyperparathyroidism (PHPT) who do not undergo parathyroidectomy. Denosumab effectively treats osteoporosis in patients with PHPT and improves hypercalcemia in the short term after administration. However, the medium-term effects of denosumab monotherapy on serum calcium levels and its safety in patients with PHPT remain unclear. In this study, we aimed to determine the medium-term effect of denosumab on serum calcium levels and bone mineral density (BMD) in patients. In this retrospective study, we compared serum calcium levels in patients with PHPT who did not undergo parathyroidectomy before denosumab monotherapy, 3 and 6 months after administration, respectively. Furthermore, we analyzed whether BMD increased 1 year after administration. Serum calcium levels in 15 patients with PHPT did not significantly change before (median serum calcium level, 10.8 mg/dL) or 6 months after denosumab administration (10.8 mg/dL). However, among 5 patients who visited the hospital for treatment of different diseases and whose serum calcium levels were measured 3 months after administration, their serum calcium levels significantly decreased after 3 months (from 10.6 to 9.8 mg/dL). No patient developed hypocalcemia. The BMD in the lumbar spine increased 12 months after denosumab administration (from 0.707 to 0.784 g/cm2). These results suggest that denosumab administration alone is safe for hypocalcemia and effective for treating osteoporosis in patients with PHPT. In addition, it can be a good treatment option for patients who do not undergo parathyroidectomy.