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Endocrine Abstracts (2019) 63 P82 | DOI: 10.1530/endoabs.63.P82

1Endocrinology Research Centre, Moscow, Russian Federation; 2Federal State Autonomous Educational Institution of Higher Education I.M. Sechenov First Moscow State Medical University of the Ministry of Health of the Russian Federation (Sechenov University), Moscow, Russian Federation.


Objective: Tumor-induced osteomalacia is a rare paraneoplastic syndrome in which fibroblast growth factor 23 (FGF-23) hyperproduction by tumor causes renal phosphate wasting, severe hypophosphatemia and osteomalacia. Localization of the tumor can be a major diagnostic challenge.

Material and methods: We present a clinical case concerning a 62-year old woman previously diagnosed with hypophosphatemic osteomalacia, with a slight improvement of clinical and laboratory manifestations after initiation of medical treatment.

Results: The patient had 10-year history of pronounced lower back pain, decrease in height by 16 cm during life, multiple atraumatic fractures of the ribs and pelvic bones. 6 years earlier she underwent surgical treatment for the mass lesion of the proximal part of the left femur (histologic examination – osteoma). She was diagnosed with hypophosphatemic osteomalacia 4 years earlier and received treatment with alfacalcidol 3 mcg/day, cholecalciferol 15 000 IU/week, calcium 1000 mg/day. The examination showed low serum P level 0.6 mmol/l (0.74–1.52), elevated PTH 111 pg/ml (15–65), normal levels of total and albumin-adjusted serum Ca, a slight increase in alkaline phosphatase (ALP) 158 IU/l (50–150) and CTx 0.836 ng/ml (0.01–0.69), 25(OH)D 23.4 ng/ml. Low tubular maximum reabsorbtion of phosphate corrected for glomerular filtration rate (TmP/GFR) 0.45 indicated renal phosphate wasting. Considering likely ectopic hyperproduction of FGF-23, we performed whole body scintigraphy with somatostatin analogue, which revealed focal intensive radiotracer uptake in left inguinal region. CT scan of the pelvic area excluded the presence of a primary focus in the area of a previously removed osteoma. After tumor-removal surgery, follow-up blood test on the 3rd day showed normalization of serum P level. Four months after surgical procedure, P level remained within the normal range, TmP/GFR showed no renal phosphate wasting. Ca level also remained within the normal range, while elevation of ALP 209 IU/l (40–150) as well as PTH 99 pg/ml (15–65) was observed, 25(OH)D 20.4 ng/ml. Marked elevation of osteocalcin 153 ng/ml (11–43) and CTx 2.34 ng/ml (0.01–0.69) suggested intense bone remodeling. Therapy with alfacalcidol, cholecalciferol and calcium was continued with increase of calcium dose up to 2000 mg/day.

Conclusion: The diagnosis of tumor-induced osteomalacia is challenging and is commonly delayed for years. Attention to biochemical values (especially serum P level) and thorough use of imaging techniques are the key steps. Only surgical removal of causative tumor can provide complete cure.

Volume 63

21st European Congress of Endocrinology

Lyon, France
18 May 2019 - 21 May 2019

European Society of Endocrinology 

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