Development of lumbar bone mineral density in the late course after kidney transplantation

Background: Rapid bone loss is a frequent finding early after kidney transplantation. Only limited data are available on the bone mineral density (BMD) in long-term kidney transplant recipients. Methods: In 26 kidney transplant recipients (13 men and 13 women, age 45.3 +/- 12.3 years), serum biochemical markers of bone metabolism and BMD at the lumbar vertebrae L2-4 were evaluated prospectively in three serial examinations (E1, E2, E3; method: dual-energy X-ray absorptiometry). Examinations were performed at 47 +/- 2 months, 59 +/- 2 months, and 71 +/- 2 months after transplantation. All patients received standard dual or triple immunosuppression including prednisolone. Results: The mean BMD was significantly lower (P < 0.001) than in sex-matched young controls: T-score was -1.43 +/- 1.49 (E1), -1.39 +/- 1.40 (E2), and -1.44 +/- 1.30 (E3). The BMD did not change significantly (Δ BMD, -0.5 +/- 5.9%) from E1 to E3. Regression analysis did not show significant associations between Δ BMD and biochemical parameters or prednisolone dosage. No clinically apparent new lumbar vertebral fracture occurred. The mean intact parathyroid hormone was 110.1 +/- 97.5 pg/mL (E1), 121 +/- 102.7 pg/mL (E2), and 134.5 +/- 128.6 pg/mL (E3). Serum creatinine was 1.44 +/- 0.45 (128 +/- 40) mg/dL (μmol/L) (E1), 1.44 +/- 0.47 (127 +/- 42) mg/dL (μmol/L) (E2), and 1.45 +/- 0.70 (128 +/- 62) mg/dL (μmol/L) (E3). Ten patients (38.5%) showed an increase of BMD (+5.7 +/- 3.2%) and 15 patients (57.7%) showed a decrease of -4.7 +/- 3.2% (P < 0.0001). Both groups were different in T-scores at E1 (-2.29 +/- 1 versus -0.88 +/- 1.5); intact parathyroid hormone, creatinine, vitamin D levels, and prednisolone dosage were not significantly different. Conclusion: This study shows that lumbar BMD is reduced in long-term kidney transplant recipients. During our 24-month observation period, overall lumbar BMD remained stable.