Serum changes in fibroblast growth factor-23 and in parameters of phosphorus metabolism after renal transplantation

Background Kidney transplantation is the preferred treatment for chronic kidney disease, but its effect on disordered mineral metabolism is incompletely understood. Post-transplant mineral bone disease (MBD) is an important complication, although its etiology and course vary. Fibroblast growth factor (FGF23) controls phosphate and vitamin D metabolism, and its assessment increases our understanding the pathogenesis of post-transplant bone disease.Aim To determine the regulation of serum FGF23 in relation to other biochemical parameters in our post-transplant participants with preserved renal function.Materials and methods A case–control study conducted on 48 kidney transplant recipients, with age ≥ 18 years old and an estimated glomerular filtration rate (eGFR) > 60 ml/min/1.73m2, from the different transplantation centers during their follow-up from 2015 to 2016. They classified in equal number according to their post-transplant follow-up period into: group A; early 6 months, and group B; late 6 months. In addition, 20 healthy persons were enrolled in the study as controls. Patients with graft rejection at the time of enrollment, those with infections and neoplasms or taking medications were excluded. Participants subjected to full history taking and clinical examination. Peripheral hemogram, blood glucose, lipid profile, liver function, kidney function, urine analysis, calcium, phosphorus, parathyroid hormone (PTH), 25-hydroxyvitamin D, FGF23, and 24-h urinary phosphorus were done.Results Significantly high levels of FGF23, PTH, and urinary phosphorous (108.6±92.7 pg/ml, 150.7±51 pg/ ml, and 1170.5±331.1 mg/day with P<0.001 for each) with significant low levels of serum phosphorus and vitamin D3 (2.5±0.9 mg/dl and 21.1±11.4 ng/ml with P<0.001 for each) in early 6-month post-transplant period were found in our patients. However, Nearly equal non-significant levels of corrected serum calcium were found throughout the study. Multivariate linear regression analysis showed significant associations of FGF23 with eGFR and other mineral bone indices in patients groups, with P˂0.05. Receiver operating characteristic curve showed that PTH of high sensitivity and specificity (95.83 and 83.33%, respectively) and phosphaturia of high sensitivity but low specificity (91.67 and 58.33%, respectively) not FGF23 (had low sensitivity and specificity (54.17 and 33.33%, respectively) could be considered as independent markers to regulate MBD in the early post-transplant period.Conclusion FGF23 may play a role in the pathogenesis of MBD in post-transplanted patients. Although, significant associations of FGF23 with other conventional bone mineral indices in early 6-month post-transplant period were confirmed, it could not be considered as an independent marker to regulate MBD in the early post-transplant period. Future prospective studies with larger numbers of transplant recipients are required to establish its direct relationship with development or severity of MBD.