What is Tumor-Induced Osteomalacia?

Tumor-induced osteomalacia (TIO) is a rare disease caused by typically benign, slow-growing tumors that produce excess levels of FGF23, which is involved in phosphate reabsorption. Patients with TIO can experience symptoms including severe hypophosphatemia (low levels of phosphate in the blood), osteomalacia (softening of the bones), muscle weakness, fatigue, bone pain and fractures.

There are an estimated 500 to 1,000 people in the United States with TIO, and approximately half of all cases are believed to be inoperable. 


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