Rare Bone Diseases-Hypophosphatemic Disorders

Video Transcription

Video Summary

This video is a part of the Endocrine Society's fellow training series on Rare Bone Diseases. The focus of this section is on hypophosphatemic disorders. The objectives include understanding FGF23, managing hypophosphatemic rickets, and identifying the most common genetic mutation.<br /><br />FGF23 is primarily produced by osteocytes when there are elevated levels of serum phosphate, vitamin D, and PTH. It binds to receptors in the kidney tubules, leading to reduced expression of sodium phosphate transporters and increased urinary excretion of phosphorus. Elevated FGF23 also inhibits the production of active vitamin D, which reduces phosphate absorption from the gut. This results in hypophosphatemia, leading to osteomalacia, bone pain, fractures, and muscle weakness.<br /><br />Hereditary hypophosphatemic rickets is characterized by low serum phosphorus, high urinary phosphorus, high or normal PTH, and high FGF23 levels. The most common inheritance pattern is X-linked dominant, and the primary treatment is calcitriol and phosphate supplements.<br /><br />Tumor-induced osteomalacia is a rare condition caused by tumors that produce excess FGF23. It presents with osteomalacia, renal phosphate wasting, low serum vitamin D, and elevated FGF23 levels. Diagnostic imaging techniques include DOTATATE scan, PET-CT, and Octreotide scan.<br /><br />Overall, the video provides information on the pathophysiology, diagnosis, and treatment of hypophosphatemic disorders, including hereditary hypophosphatemic rickets and tumor-induced osteomalacia.

Keywords

FGF23

hypophosphatemic rickets

genetic mutation

osteomalacia

tumor-induced osteomalacia


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