Primary Hyperparathyroidism with Severe Vitamin D Deficiency in Chronic Kidney Disease

A 71-year-old woman with altered consciousness was diagnosed with primary hyperparathyroidism (PHPT) after presenting with severe hypercalcemia (serum Ca 15.3 mg/dL) and parathyroid adenoma. Unusually, her 1,25 (OH) ₂D₃ level was undetectable, despite PHPT. Hemodialysis and evocalcet failed to control the calcium levels, but denosumab effectively reduced hypercalcemia. However, both 25 (OH) D₃ and 1,25 (OH) ₂D₃ remained low. This case highlights the importance of vitamin D assessment in PHPT, as its metabolism can vary. Denosumab may be a viable treatment option for calcimimetic hypercalcemia.