Endocrine Abstracts

Tumor-induced osteomalacia (TIO) is a rare paraneoplastic syndrome of abnormal phosphate metabolism caused by a small mesenchymal tumor that secrete fibroblast growth factor 23 (FGF23). A 29-year-old female has suffered from two low-traumatic hip fractures, multiple fractures at the pelvic and sacrum, and diffuse bone pain for more than 3 years. Her mobility was limited in the last year (used crutches) because she had severe muscle weakness. Laboratory examination at the time of admission showed serum phosphate – 0.4 mmol/l (0.87–1.45), alkaline phosphatase 490 U/l (50–150), tubular reabsorption of phosphate (TRP) 45% (85–95%). Somatostatin receptor scintigraphy with 99 mTc-HYNIC-TOC revealed subcutaneous tumor in the left femur. CT scan confirmed the location of a tumor in the proximal left femur, 10×11×29 mm in size. The patient had complete recovery in phosphate levels the next day after surgical treatment, which remained within the reference range after 6 months of follow-up. The clinical improvement was evident after 3 months of observation when the patient fully restored the normal ability to walk without crutches. Histopathology confirmed mesenchymal tumor. A 34-year-old female suffered from bone pain, muscle weakness and decrease in height by 20 cm more than 8 years. At the age of 31, the patient developed two low-traumatic hip fractures and multiple vertebral fractures. The routine investigation at the time of admission revealed: serum phosphate 0.54 mmol/l (0.87–1.45), alkaline phosphatase 656 U/l (50–150), TRP 57.5% (85–95%). Somatostatin receptor scintigraphy with 99 mTc-HYNIC-TOC showed lesion in the subcutaneous tissue of left hip. CT scan confirmed the location of the tumor, 30 mm in diameter. Surgical treatment was effective for phosphate normalization and clinical improvement of the patient. Conclusion: tumor-induced osteomalatia should be suspected in young patients with fragility fractures. Serum phosphate and tubular reabsorption phosphate measurements along with somatostatin receptor scintigraphy with 99mTc-HYNIC-TOC are sufficient for TIO diagnostics with a good prognosis after successful treatment.