Lower serum fibroblast growth factor-23 levels may suggest malnutrition in maintenance haemodialysis patients

Aim It is reported that high serum fibroblast growth factor-23 (FGF-23) levels are associated with increased mortality in haemodialysis patients, and can be caused by hyperphosphataemia and loss of residual renal function. However, hypophosphataemia is also associated with increased mortality in maintenance haemodialysis (MHD) patients. We studied the determinants of the serum FGF-23 levels in MHD patients, focusing on nutritional status and residual renal function. Methods A total of 332 Japanese MHD patients with a median age of 69 years, and median dialysis vintage of 66 months, were studied. The serum levels of intact FGF-23, albumin, phosphate, and intact parathyroid hormone (iPTH), corrected serum calcium (Ca) levels, urine volume, (creatinine clearance + urea clearance)/2, phosphate clearance, Kt/Vurea, body mass index (BMI), normalized protein catabolic rate (nPCR), normalized protein equivalent of nitrogen appearance (nPNA), geriatric nutritional risk index (GNRI), and the prescribed dosages of active vitamin D and phosphate binders were assessed. Results The significant independent factors for InFGF-23 by multivariate analysis were age, GNRI, serum phosphate, Ca, iPTH levels and dosage of active vitamin D in patients without residual renal function (P < 0.05). Among all MHD patients, the lowest BMI, nPNA, nPCR, GNRI, serum albumin, creatinine, phosphate, Ca, Ca x P product and iPTH values were seen in the lowest serum FGF-23 quartile (FGF-23 < 311 pg/mL). Conclusions The determinants of the serum FGF-23 level in MHD patients without residual renal function were age, serum phosphate, Ca, iPTH levels, the active vitamin D dose and the GNRI. The lower serum FGF-23 levels may suggest malnutrition in MHD patients.