Hypophosphatemic Osteomalacia: Association with Prostatic Carcinoma

Abstract

Hypophosphatemic osteomalacia that remits after resection of a coexisting tumor is described in 35 patients. Because the associated neoplasms were of mesenchymal origin, it was inferred that this tumor-induced osteomalacia syndrome is uniquely related to tumors of this derivation. Subjects with coincident hypophosphatemia and prostatic carcinoma were studied to ascertain whether this endodermal malignancy causes the tumor-induced osteomalacia syndrome. The hypophosphatemic patients had renal phosphate wasting, gastrointestinal malabsorption of Ca and phosphate, and negative phosphate balance. Bone biopsies showed histomorphologic changes indicative of osteomalacia. Although widespread metastases precluded establishing the diagnosis of tumor-induced osteomalacia by resection of the tumor, a series of studies excluded alternate causes for the osteomalacia. Affected subjects had a normal serum concentration of 25-hydroxyvitamin D, 28.0 .+-. 8.3 ng/ml, and serum 1,25-dihydroxyvitamin D levels were low, 15.0 .+-. 1.0 pg/ml, characteristic of the tumor-induced osteomalacia syndrome. Prostatic carcinoma, although an endodermal maligancy may cause the tumor-induced osteomalacia syndrome.