Early changes in bone mass, biochemical bone markers and fibroblast growth factor 23 after renal transplantation.

Background: Serum osteocalcin and C-terminal telopeptides of type-1 collagen (CTX-1) are known markers of bone turnover, whereas the role of fibroblast growth factor 23 (FGF-23) is yet unknown. We investigated early changes in bone mass and the association of these biochemical markers and FGF-23 with bone loss following renal transplantation (RTx).

Material And Methods: In 44 first-kidney allograft patients, BMD was measured by dual-energy X-ray absorptiometry in the lumbar spine (LS), total femur (TF) and total body (TB) at baseline and 10 weeks post-transplant. Serum osteocalcin, CTX-1, intact FGF-23, intact parathormone (iPTH) and 25-hydroxyvitamin D (25-OHD) levels were measured. Associations were tested by correlation and multiple linear regression.

Results: We found a significant (p<0.05) decrease in bone mass in LS (2.6 %), TF (2.1 %) and TB (1.4 %). Osteocalcin (0.95 versus 1.56 nmol/L) and CTX-1 (1.05 versus 1.47 ng/mL) levels increased significantly, while serum FGF-23 and iPTH decreased. Serum osteocalcin and CTX-1 were significantly associated at both baseline and follow-up. Baseline osteocalcin and CTX-1 were independently associated with bone loss in TB and TF, respectively. Neither iPTH nor 25-OHD showed consistent association with bone loss. FGF-23 was not related to change in bone mass or to biochemical markers of bone turnover.

Conclusion: Our results confirm an early decrease in bone mass with high bone resorption rate after RTx. Osteocalcin and CTX-1 are associated with bone loss in the early post-transplant period; thus, these markers may be a reasonable choice for routine assessment of bone turnover in this setting. The role of FGF-23 remains to be further elucidated.