FGF23 and hypophosphatemia: Oncogenic osteomalacia (OOM), or tumor-induced osteomalacia (TIO), is a rare paraneoplastic condition that is characterized by bone pain, muscle weakness, and osseous fractures in addition to persistent hypophosphatemia brought on by renal phosphate depletion, normal or low 1,25(OH)2D, and increased or inappropriately normal fibroblast growth factor 23.