Tumor-related osteomalacia followed after treatment by hyperparathyroidism

Tumor-induced osteomalacia is due to renal phosphate wasting in response to a humoral factor produced by a tumor, usually a benign mesenchymal tumor. Removal of the tumor is followed by resolution of the metabolic disorder. P hysicians should be aware that sporadic renal phosphate wasting in an adult should prompt a search for a tumor. A case of tumor-induced osteomalacia d ue to a nonossifying fibroma of the radius is reported. After removal of th e tumor, renal phosphate excretion returned to normal, but the patient deve loped tertiary hyperparathyroidism. Eight years elapsed between symptom ons et and the diagnosis of the tumor. The pathogenesis of tumor-induced osteom alacia and the role of treatment for renal phosphate wasting on the subsequ ent development of hyperthyroidism are discussed.