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Review
. 2014 Jun;29(2):136-43.
doi: 10.3803/EnM.2014.29.2.136.

Diagnostic Modalities for FGF23-Producing Tumors in Patients with Tumor-Induced Osteomalacia

Seiji Fukumoto  1
Affiliations
Review

Diagnostic Modalities for FGF23-Producing Tumors in Patients with Tumor-Induced Osteomalacia

Seiji Fukumoto. Endocrinol Metab (Seoul). 2014 Jun.

Abstract

Fibroblast growth factor 23 (FGF23) is a hormone that is produced by osteocytes and regulates phosphate and vitamin D metabolism through binding to the Klotho-FGF receptor complex. Excessive actions of FGF23 cause several kinds of hypophosphatemic rickets/osteomalacia. Tumor-induced rickets/osteomalacia (TIO) is a paraneoplastic syndrome caused by overproduction of FGF23 from the responsible tumors. Because TIO is cured by complete resection of the causative tumors, it is of great clinical importance to locate these tumors. Several imaging methods including skeletal survey by magnetic resonance imaging and octreotide scintigraphy have been used to identify the tumors that cause TIO. However, none of these imaging studies indicate that the detected tumors are actually producing FGF23. Recently, systemic venous sampling was conducted for locating FGF23-producing tumor in suspected patients with TIO and demonstrated that this test might be beneficial to a subset of patient. Further studies with more patients are necessary to establish the clinical utility of venous sampling in patients with TIO.

Keywords: 1,25-Dihydroxyvitamin D; Fibroblast growth factor 23; Hypophosphatemia; Sampling.

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Conflict of interest statement

No potential conflict of interest relevant to this article was reported.

Figures

Fig. 1
Fig. 1
Changes in fibroblast growth factor 23 (FGF23) levels after removal of responsible tumors for tumor-induced rickets/osteomalacia (TIO). Responsible tumors for TIO were operated on day 0 and FGF23 levels were followed for up to 7 days. FGF23 was measured by an enzyme-linked immunosorbent assay that detects full-length FGF23 with a detection limit of 3 pg/mL (The horizontal line). The shaded area indicates the reference range for FGF23 (10 to 50 pg/mL). In six patients who were cured by the operation, FGF23 became undetectable in five patients within 2 days. In addition, FGF23 was below the lower limit of the reference range on day 2 in patient 8. FGF23 increased after the initial drop in patient 1 and 2, and hypophosphatemic osteomalacia was not cured in these patients.
Fig. 2
Fig. 2
Fibroblast growth factor 23 (FGF23) levels obtained in venous sampling. FGF23 was high in patient's left external iliac vein and a tumor was found in the left femoral head. The unit of FGF23 is pg/mL.
See this image and copyright information in PMC

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