Clinical analysis of persistent hypercalcemia with osteoporosis caused by tertiary hyperparathyroidism after kidney transplantation

Objective To explore the clinical characteristics of tertiary hyperparathyroidism (THPT) after renal transplantation. Methods The levels of bone mineral density (BMD), serum calcium, phosphates, alkaline phosphatase (ALP) and intact parathyroid hormone (iPTH) were retrospectively analyzed in 36 RTx recipients with persistent hypercalcemia and stable kidney function (eGFR 76.71±17.44) ml/min/1.73 m2. Results Among them, serum total calcium level increased (2.97±0.20) mmol/L for 6 to 170 months, blood phosphorus decreased (0.59±0.19) mmol/L, serum alkaline phosphatase (ALP) increased to (295.73±194.22)U/L and T-score of BMD decreased (T-2.78±0.84 in lumbar vertebrae and T-2.09±0.66 in hip joint). And 11/36 (30.6%) cases had a complication of extraosseous calcification. Parathyroid hyperplasia was detected in 17/36 cases (47.2%). iPTH was significantly higher at pre-operation and 1 week post-operation than that in control group (n=45) (859.50±495.44 vs 345.56±216.55 pg/ml), P=0.001, (759.25±907.07 vs 197.45±249.31 pg/ml), P=0.001. The value of iPTH at the last follow-up (198.26±155.22) pg/ml was still higher than normal reference value (15.0-65.0 pg/ml). Multivariate stepwise regression analysis showed the last iPTH was correlated with preoperative iPTH, serum calcium and postoperative serum phosphor, ALP and 25OHD3 (P=0.024, P=0.002, P=0.001, P=0.037, P=0.026). Conclusions Renal recipients had a higher levels iPTH with persistent hypercalcemia, hypophosphatemia, osteoporosis and extraosseous calcification showing the features of tertiary hyperparathyroidism. Key words: Kidney transplantation; Tertiary hyperparathyroidism; Hypercalcemia; Osteoporosis