The comparison study of BMD between patients with normocalcemic and hypercalcemic hyperparathyroidism after kidney transplantation and its predictors

Abstract Introduction Persistent hyperparathyroidism is a well-established complication following kidney transplantation with a significant impact on bone health. This condition can lead to bone thinning and an elevated risk of fractures. However, a comparison between normocalcemic and hypercalcemic hyperparathyroidism is less well-studied. Objective This study aims to compare bone mineral density (BMD) values among post-kidney transplant patients with normocalcemic hyperparathyroidism and hypercalcemic hyperparathyroidism. The secondary objective is to explore clinical factors that predict BMD values and BMD changes over time in this population. Method This cross-sectional study included patients who were more than 1 year post-kidney transplant and had persistent hyperparathyroidism documented more than 2 times. Medical history, laboratory results and BMD values were collected. Results This study included a total of 130 patients, 64 (49.2%) had normocalcemic hyperparathyroidism and 66 (50.8%) had hypercalcemic hyperparathyroidism. 72 patients underwent BMD measurement. Patients in the hypercalcemic hyperparathyroidism group had higher iPTH (141.1 vs 87.3 pg/mL, P  = 0.004), higher corrected calcium (10.8 vs 9.7 mg/dL, P  < 0.001), lower phosphate (2.7 vs. 3.2 mg/dL, P < 0.001), and longer dialysis vintage (6.4 vs 4.3 years, P  = 0.010) when compared to those in the normocalcemic group. Mean BMD values in the hypercalcemic vs normocalcemic groups at all sites were similar. Female sex and longer dialysis vintage independently predicted lower BMD at multiple sites. In longitudinal analysis (n = 19), BMD changes did not differ significantly between the two groups at any skeletal site, although patients with hypercalcemia showed a trend toward greater cortical bone loss. Conclusion Among post-kidney transplant patients with persistent hyperparathyroidism, BMD and BMD changes were similar between those with hypercalcemic and normocalcemic hyperparathyroidism. Dialysis vintage and female sex were primary predictors of lower BMD.