Combined treatment by burosumab and a calcimimetic can ameliorate hypophosphatemia due to excessive actions of FGF23 and PTH in adult XLH with tertiary hyperparathyroidism: A case report

Front Endocrinol (Lausanne). 2022 Dec 2:13:1004624. doi: 10.3389/fendo.2022.1004624. eCollection 2022.


Introduction: X-linked hypophosphatemia (XLH) is the most prevalent type of heritable fibroblast growth factor 23 (FGF23)-related hypophosphatemic rickets. Recently, anti-FGF23 antibody, burosumab, has become clinically available. We herein report a patient with adult XLH and tertiary hyperparathyroidism.

Case presentation: The serum phosphate level and tubular maximum reabsorption of phosphate per glomerular filtration rate (TmP/GFR) remained low, despite burosumab treatment. While the influence of the relationship between FGF23 and parathyroid hormone (PTH) on the phosphaturic effect is unclear, it was considered that a high level of PTH due to tertiary hyperparathyroidism remains to suppress renal phosphate reabsorption. A calcimimetic, evocalcet, increased the serum phosphate level and TmP/GFR.

Discussion and conclusion: Therefore, it is important to evaluate the presence of secondary-tertiary hyperparathyroidism in patients whose serum phosphate level does not increase with burosumab treatment.

Keywords: X-linked hypophosphatemia; burosumab; evocalcet; fibroblast growth factor 23; parathyroid hormone; tertiary hyperparathyroidism.

Publication types

  • Case Reports

MeSH terms

  • Adult
  • Familial Hypophosphatemic Rickets* / complications
  • Familial Hypophosphatemic Rickets* / drug therapy
  • Fibroblast Growth Factors / metabolism
  • Humans
  • Hyperparathyroidism*
  • Hypophosphatemia* / drug therapy
  • Hypophosphatemia* / etiology
  • Parathyroid Hormone
  • Phosphates


  • Parathyroid Hormone
  • burosumab
  • Fibroblast Growth Factors
  • Phosphates