FGF23 elevation and hypophosphatemia after intravenous iron polymaltose: a prospective study

Area of Science:

• Endocrinology
• Nephrology
• Mineral Metabolism

Background:

• Parenteral iron is linked to hypophosphatemia.
• Fibroblast growth factor 23 (FGF23) regulates phosphate homeostasis.
• Previous findings suggest a link between iron, FGF23, and hypophosphatemia.

Purpose of the Study:

• To prospectively investigate the impact of parenteral iron polymaltose on phosphate homeostasis.
• To determine if changes in phosphate homeostasis are related to FGF23 alterations.

Main Methods:

• Eight outpatients received intravenous iron polymaltose.
• Measurements included plasma phosphate, 25-hydroxyvitamin D [25(OH)D], 1,25-dihydroxyvitamin D [1,25(OH)(2)D], PTH, FGF23, and urinary phosphate reabsorption.
• Data were collected at baseline and weekly for at least 3 weeks.

Main Results:

• Plasma phosphate and tubular reabsorption of phosphate significantly decreased post-iron administration.
• 1,25(OH)(2)D levels dropped significantly, while 25(OH)D levels remained unchanged.
• FGF23 levels markedly increased, correlating with decreased serum phosphate and 1,25(OH)(2)D.

Conclusions:

• Parenteral iron impairs renal phosphate reabsorption and vitamin D activation, leading to hypophosphatemia.
• Increased FGF23 levels appear to mediate these effects.
• This study elucidates the mechanism of iron-induced hypophosphatemia.