Effects of Denosumab and Calcitriol on Severe Secondary Hyperparathyroidism in Dialysis Patients With Low Bone Mass

Context: Secondary hyperparathyroidism (SHPT) may worsen with administration of denosumab in chronic renal failure patients with low bone mass. Objective: This study aimed to evaluate the short-term effect of coadministration of calcitriol and denosumab on PTH secretion and parathyroid structure and the incidence of adverse effects in patients with SHPT and low bone mass. Design and Setting: This was a 24-week, open-label study at Kaohsiung Veterans General Hospital in Kaohsiung, Taiwan. Patients: Dialysis patients with SHPT (intact parathyroid hormone [iPTH] > 800 pg/mL) and low bone mass (T score < -2.5) were enrolled. Intervention: Patients received denosumab (60 mg) and doses of calcitriol adjusted to achieve iPTH < 300 pg/mL. Main Outcome Measures: Parathyroid gland volume was assessed upon study initiation and completion. Serum calcium, phosphate, alkaline phosphatase, iPTH, and adverse effects were assessed at each visit (Day 7, 14, and 21, and every month thereafter). Results: iPTH significantly decreased (mean decrease, 58.28 +/- 6.12%) with denosumab/calcitriol administration (P < .01) but not in the controls (patients not receiving denosumab). Parathyroid gland volume decreased (mean decrease, 21.98 +/- 5.54%) with denosumab/calcitriol administration (P < .01) and progressively increased (20.58 +/- 4.48%) in the controls (P < .05). Serum alkaline phosphatase and iPTH levels were significantly correlated to decreased iPTH and regression of parathyroid hyperplasia (P < .05). The most common adverse events were hypocalcemia(33.33%) and respiratory tract infection (4.17%). Hypocalcemia rapidly resolved with calcium and calcitriol supplements. Conclusions: Denosumab allows for supra-physiologic doses of calcitriol resulting in decreased parathyroid secretion and parathyroid hyperplasia. Supervised administration and weekly laboratory and clinical monitoring of serum calcium are recommended during the first month to prevent hypocalcemia.