In some TIO patients with normal FGF23 levels, one may consider hypophosphatemia driven by a different paraneoplastic phosphaturic hormone, or whether FGF23 secretion may be partially responsive to serum phosphate levels in some tumors.(23) For example, matrix extracellular phosphoglycoprotein, secreted frizzled protein 4, and FGF‐7 are all additional phosphatonins that have rarely been associated with TIO.(12, 28). This evidence concerns the gene FGF23 and hypophosphatemia.