title: Hypophosphatemia related to paraneoplastic Cushing syndrome in prostate cancer: cure after bilateral adrenalectomy.
abstract: We report the case of a 71-year-old man with progressive metastatic prostate cancer in whom simultaneous occurrence of paraneoplastic Cushing syndrome (CS) and tumor-induced osteomalacia (TIO) initially was suspected. However, the evolution of biochemical markers of phosphate metabolism during disease course and after bilateral adrenalectomy argued against the diagnosis of TIO. Despite the persistence of progressive prostate cancer, CS and hypophosphatemia resolved in parallel after bilateral adrenalectomy. Thus, these data suggest that paraneoplastic CS per se was involved in the pathogenesis of hypophosphatemia. Calcitriol and intact fibroblast growth factor 23 (FGF23) levels were within the reference range at onset, which is inappropriate in the setting of severe hypophosphatemia. All parameters of phosphate metabolism normalized after resolution of hypercortisolism. Based on the known suppressive effect of glucocorticoids (GCs) on bone remodeling and the inverse relationship between bone turnover rate and circulating FGF23 levels, we postulate that GCs interfere indirectly with phosphate homeostasis by inducing inappropriate FGF23 production and release. This mechanism could further aggravate the hypophosphatemia resulting from GC-induced inhibition of intestinal phosphate absorption. Studies directed at the identification of the molecular pathways in bone mediating the interference of GCs with phosphate metabolism are warranted.
authors: Department of Internal Medicine-Endocrinology, University Hospital Brugmann, Free University of Brussels, Belgium. iramon06@hotmail.com
authors: Isolde
authors: I
authors: Ramon
authors: Pierre
authors: P
authors: Kleynen
authors: Joseph
authors: J
authors: Valsamis
authors: Jean-Jacques
authors: JJ
authors: Body
authors: Rafik
authors: R
authors: Karmali
mesh_terms: D000315:Adrenalectomy; D000368:Aged; D002117:Calcitriol / Q000378:metabolism; D003480:Cushing Syndrome / Q000150:complications*; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors / Q000378:metabolism; D006801:Humans; D017674:Hypophosphatemia / Q000209:etiology / Q000628:therapy*; D008297:Male; D010257:Paraneoplastic Syndromes / Q000150:complications*; D011471:Prostatic Neoplasms / Q000150:complications* / Q000473:pathology
chemical_list: C000717427:FGF23 protein, human; D005346:Fibroblast Growth Factors; D000089703:Fibroblast Growth Factor-23; D002117:Calcitriol