Excess FGF23
FGF23 is a protein hormone produced by osteocytes in the bones that regulates serum phosphorus levels. Loss-of-function PHEX gene variants cause excess FGF23 levels, according to animal studies.2-4
Mechanism of disease and CRYSVITA Mechanism of Action1†
In XLH, increased serum levels of FGF23 are the underlying cause of chronic hypophosphatemia1-3
Reduced renal phosphorus reabsorption
Excess FGF23 can result in excess phosphorus excretion in the urine.3
Reduced renal production of active vitamin D
Excess FGF23 also suppresses active vitamin D production.2-4
Chronic hypophosphatemia2
Excess FGF23
FGF23 is a protein hormone produced by osteocytes in the bones that regulates serum phosphorus levels. Loss-of-function PHEX gene variants cause excess FGF23 levels, according to animal studies.2-4
Reduced renal phosphorus reabsorption
Excess FGF23 can result in excess phosphorus excretion in the urine.3
Reduced renal production
of active vitamin D
Excess FGF23 also suppresses active vitamin D production.2-4
Chronic hypophosphatemia2
Inhibition of biological activity of FGF23 with CRYSVITA increases renal phosphate reabsorption and serum concentration of 1,25 dihydroxy-vitamin D1†
Binding and inhibition of excess FGF23
Increased renal phosphate reabsorption1
Increased serum 1,25 dihydroxy-vitamin D concentration1
CRYSVITA is the FIRST AND ONLY FGF23 inhibitor indicated in XLH1,5‡
FGF23=fibroblast growth factor 23.
† Clinical significance is unknown.
‡ Comparative clinical significance has not been established.
References: 1. CRYSVITA (burosumab injection) Product Monograph. Kyowa Kirin Inc. March 15, 2023. 2. Glorieux FH, et al. Potential influences on optimizing long-term musculoskeletal health in children and adolescents with X-linked hypophosphatemia (XLH). Orphanet J Rare Dis. 2022;17(1):30. 3. Dahir K, et al. X-linked hypophosphatemia: A new era in management. J Endocr Soc. 2020;4(12):bvaa151. 4. Haffner D, et al. Clinical practice recommendations for the diagnosis and management of X-linked hypophosphataemia. Nat Rev Nephrol. 2019;15(7):435-455. 5. Data on file. First and only claim. Kyowa Kirin Inc.