Evolution of Bone Disease at 2 Years After Transplantation: A Single-Center Study

Abstract

Posttransplant bone disease is caused by renal osteodystrophy. We sought to examine bone mineral density (BMD) among 90 renal allograft recipients of mean age 42.7 ± 11.4 years to identify factors preventing bone loss at 2 years posttransplant. Subjects treated with cyclosporine or tacrolimus plus azathioprine/MMF and prednisone underwent BMD estimates of the lumbar spine (LS) and of the proximal femur using dual energy x-ray absorptiometry (DEXA) at 3 months and every 6 months for 2 years. We assayed markers of bone remodeling: intact parathyroid hormone (iPTH), calcitriol, osteocalcin, and carboxyterminal telopeptide of type I collagen on day 3, as well as month 1 and every 6 months after transplantation. At the initial measurement, we observed osteopenia (OSP) among 35% in the LS and 52% in the femur: there was osteoporosis in 8.3%. The prevalence of OSP increased during the first year, thereafter decreasing to the initial value, but the rate of osteoporosis did not change significantly (8.3% vs 6.0%). BMD and Z-score decreased during the first and increased in the second year; 27% of patients regained initial values and 38% higher ones. BMD gains in the LS and femur were observed among subjects with higher calcitriol levels during the first 6 months ( P < .01), higher osteocalcin ( P < .05), higher estimated glomerular filtration rate during 1–24 months and in the tacrolimus group. Improvement of LS BMD occurred in younger patients (38 vs 46 years; P < .027); BMD gain in the femur correlated with higher levels of iPTH from 1–12 months ( P < .01). The tacrolimus group showed higher Z-scores in the LS and femur at 24 months ( P < .05). Two years after transplantation >60% of recipients showed stabilization or gain in bone mass. A sufficient calcitriol level in the early transplant period, an adequate iPTH, good renal function, and tacrolimus therapy prevented BMD disease progression.