Tumor-induced osteomalacia (TIO) is a rare paraneoplastic syndrome characterized by ectopic fibroblast growth factor-23 (FGF23) production. We report a unique case of a 78-year-old female patient with refractory hypophosphatemia. ultimately diagnosed as TIO. in the context of two metastatic primary lung cancers: adenocarcinoma and SCLC. https://foldlyers.shop/product-category/solid-state/