Sequential changes of biochemical bone parameters after kidney transplantation

Area of Science:

• Nephrology
• Endocrinology
• Bone Metabolism

Background:

• Persistent hyperparathyroidism is a known complication after kidney transplantation (Rtx).
• Previous studies had limited follow-up or infrequent measurements of biochemical bone parameters.
• This study prospectively evaluated bone parameters at short intervals for two years post-Rtx.

Purpose of the Study:

• To prospectively assess biochemical bone parameters in kidney transplant recipients over two years.
• To investigate the relationship between graft function, vitamin D levels, and parathyroid hormone (PTH) in these patients.

Main Methods:

• 129 kidney transplant recipients were monitored for biochemical bone parameters at 2, 3, 5, 8, 12, 18, and 24 months post-Rtx.
• Patients received standard immunosuppression (prednisone, cyclosporine A, azathioprine) without calcium, phosphorus, or vitamin D supplementation.
• Serum creatinine, calcium, phosphorus, alkaline phosphatase (AP), bone-specific alkaline phosphatase (BAP), osteocalcin (OC), PTH, and 25(OH)D levels were measured.

Main Results:

• Serum creatinine improved post-Rtx, while phosphorus remained in the lower normal range.
• Hypercalcemia was observed in 52% of patients at 3 months, gradually decreasing thereafter.
• Significant increases in AP, BAP, and OC were noted between 2-5 months (P < 0.001), with AP and BAP normalizing by 12 months, but OC remained elevated.
• Elevated PTH levels correlated with impaired graft function (serum creatinine) and low 25(OH)D levels (P < 0.01).
• 1,25(OH)2D3 levels increased significantly by 12 months.

Conclusions:

• Hypercalcemia is common early post-Rtx, likely due to increased PTH action and vitamin D 1-hydroxylation.
• Bone turnover markers rise significantly between 3-5 months, normalizing by one year.
• Persistent elevated PTH is linked to impaired graft function and suboptimal 25(OH)D levels.