AbstractAimDespite its importance in bone and cardiovascular disease in subjects with kidney disease, there are no data on fibroblast growth factor 23 (FGF23) perturbations in nephrotic syndrome. We evaluated FGF23 and markers of mineral bone metabolism in subjects with untreated NS.MethodsIn this cross‐sectional study, we measured circulating levels of FGF23, 25‐hydroxy vitamin D [25(OH)D], 1,25 di‐hydroxy vitamin D [1,25(OH)2D], serum albumin, serum calcium, phosphorus, creatinine and intact parathyroid hormone (iPTH) in 101 patients with adults onset NS and 40 healthy controls. We examined the correlation between FGF23 and markers of mineral bone metabolism.ResultsCompared to healthy controls, subjects with NS showed reduced levels of 25(OH)D (21.76 ± 10.18 vs 35.74 ± 40.27 nmol/L, P = 0.001), 1,25(OH)2D (median; 37.80 vs 73.13 pmol/L, P = 0.0001) and FGF23 (37.81 ± 20.42 vs 48.20 ± 11.60 pg/mL, P = 0.004) levels. Serum phosphorus levels were marginally, but significantly higher in subjects with nephrotic syndrome compared to healthy controls (P = 0.004). Serum iPTH levels were significantly higher in subjects with NS compared to healthy controls (52.24 ± 39.58 vs 37.90 ± 14.60 pg/mL, P = 0.028).ConclusionsWe conclude that FGF23 is reduced in subjects with NS compared to healthy controls. The reduced levels of Vitamin D, and urinary losses may contribute to lower levels of FGF23 in NS.