Abstract: Background: Over the past decade, our under-standing of phosphate homeostasis has increased through
the identification of phosphatonins. First case of Iron – induced hyphosphatemic osteomalacia associated with
significant FGF23 elevation was reported in 2009. Patients and Methods: 47 patients on regular HD (Group A) and
12 CKD patients stages 3 & 4 (Group B) were included in the study.For each patient the following was done: serum
calcium, serum phosphorus, calcium – phosphorus product, serum alkaline phosphatase, PTH, FGF23, serum Iron,
serum ferritin, Hb, Hct, TSAT, and TIBC. Results: PTH was higher than recommended range in both Group A and
Group B. FGF23 was also higher than normal in the two groups, and it was affected by serum creatinine in Group A
in Multiple Regression Analysis (P = 0.03136). FGF23 didn`t have any relationship to phosphate or PTH in our
study. PTH had a positive correlation to Hb (P = 0.052) and serum ferritin (P = 0.009) in HD patients group A but
not in CKD group B patients. Iron, Hb & TSAT had an inverse correlation to FGF23 in CKD patients group B (P =
0.028, P = 0.044, P = 0.025 respectively), but not in HD patients group A. Conclusion: PTH and phosphate are not
the only factors affecting FGF23 in CKD and HD patients, but also Iron and Iron parameters have a great impact on
FGF23 serum level.