The relationship between serum FGF-23 levels with vitamin D, calcium, phosphorus, lipid and bone diseases in renal transplant patients

Introduction and Purpose: Post-transplant bone diseases are frequently seen complications. In post-transplant period, development of osteoporosis and osteopenia or existing osteoporosis can be deteriorated and due to the fact that it may increase the risk of bone fractures, is known. Including initially corticosteroids, immunosuppressive agents, particularly resistant hyperparathyroidism, the ongoing high levels of serum FGF-23, vitamin D deficiency, graft dysfunction and various factors, are risk factors for bone disease. Today, studies conducted with FGF-23, made curiosity of the impact on mineral and bone disorders of FGF-23 in CKD and kidney transplant recipients but this topic has not yet been adequately studied. In this study, especially in the kidney transplant recipients, we aimed to investigate the relationship between serum FGF-23 levels and bone diseases. Materials and Methods: In this study, 109 renal transplant recipients and 30 control patients were included who are followed by Çukurova University Medical Faculty Nephrology department. Patients' age, sex, weight, height, renal failure etiology, type of dialysis before transplantation, duration of dialysis, transplant duration, types of donors, type of drugs and immunosuppressive therapy, physical examination findings were recorded. Complete blood count, creatinine clearance, lipid profile, PTH, serum and urine Ca, P levels were measured. 25OHD3, DEXA bone mineral density (BMD) were evaluated. Simultaneously taken blood serums were preserved in -80 oC until measurement of serum FGF-23 levels. Findings: The mean age of 109 renal transplant recipients (33 female, 76 male), 40,1 ± 11,1, and with 30 (15 females and 15 males) control patients it was 39,2 ±11,3. Incidence of osteopenia and osteoporosis in renal transplant recipients were significantly higher than the control group. BMD was correlated positively with body mass index, duration of renal transplantation and creatinine clearance and negatively with age and ALP. In our study, FGF-23 levels between the study group and the control group, were not shown statistically significant difference. There was positive correlation between FGF-23 and kidney transplant period, and negative correlation between FGF-23 and creatinine clearance, while the patients with lower FGF-23 levels, had significantly higher levels of ALP and 25OHD3. In our study, there was statistically significant relationship lipid profile with BMD, serum levels of PTH and 25OHD3, corticosteroids and calcineurin inhibitors. Results: The use of immunosuppressive agents, resistant secondary hiperparathyroidizm, osteomalacia, FGF-23, hypophosphatemia, renal tubular acidosis, and glomerular filtration rate of below 70 ml/min are important risk factors for post-transplant bone disease. The lack of an independent relationship between FGF-23 and bone mineral parameters is suggested as not effective alone in the pathogenesis of bone disease after renal transplantation. Bone and mineral metabolism disorders are common in kidney transplant recipients and also continues in the late periods. Kidney transplant recipients, compared to controls with similar creatinine clearance, a very high proportion of more than 75% were found osteopenia or osteoporosis. While no increase in urinary excretion of P compared to controls, serum phosphorus was found significantly lower in renal transplant recipients. Abnormal levels of Ca, P, vitamin D and PTH levels, vitamin D deficiency and hyperparathyroidism can also cause increased bone lesions. In recent years, the association of bone lesions with high salt excretion is noteworthy. Interestingly, urinary excretion of Na was > 150mEq / day in our patients. Also high levels of TG and LDL are associated with drugs and BMD. The loss of kidney function after transplantation was correlated with bone lesions. Thus, in renal transplant recipients, there is a significant reduction in BMD early period as well as the late period and there is a lot of factor to blame in pathogenesis. It can be said that renal transplant patients have higher risk for bone diseases as cardiovascular complications.