title: Calcium deficiency reduces circulating levels of FGF23.
abstract: Fibroblast growth factor (FGF) 23 inhibits calcitriol production, which could exacerbate calcium deficiency or hypocalcemia unless calcium itself modulates FGF23 in this setting. In Wistar rats with normal renal function fed a diet low in both calcium and vitamin D, the resulting hypocalcemia was associated with low FGF23 despite high parathyroid hormone (PTH) and high calcitriol levels. FGF23 correlated positively with calcium and negatively with PTH. Addition of high dietary phosphorus to this diet increased FGF23 except in rats with hypocalcemia despite high PTH levels. In parathyroidectomized rats, an increase in dietary calcium for 10 days increased serum calcium, with an associated increase in FGF23, decrease in calcitriol, and no change in phosphorus. Also in parathyroidectomized rats, FGF23 increased significantly 6 hours after administration of calcium gluconate. Taken together, these results suggest that hypocalcemia reduces the circulating concentrations of FGF23. This decrease in FGF23 could be a response to avoid a subsequent reduction in calcitriol, which could exacerbate hypocalcemia.
authors.affiliation: Research Unit, IMIBIC, Hospital Universitario Reina Sofia, Cordoba, Spain.
authors.forename: María E
authors.initials: ME
authors.lastname: Rodriguez-Ortiz
authors.forename: Ignacio
authors.initials: I
authors.lastname: Lopez
authors.forename: Juan R
authors.initials: JR
authors.lastname: Muñoz-Castañeda
authors.forename: Julio M
authors.initials: JM
authors.lastname: Martinez-Moreno
authors.forename: Alan Peralta
authors.initials: AP
authors.lastname: Ramírez
authors.forename: Carmen
authors.initials: C
authors.lastname: Pineda
authors.forename: Antonio
authors.initials: A
authors.lastname: Canalejo
authors.forename: Philippe
authors.initials: P
authors.lastname: Jaeger
authors.forename: Escolastico
authors.initials: E
authors.lastname: Aguilera-Tejero
authors.forename: Mariano
authors.initials: M
authors.lastname: Rodriguez
authors.forename: Arnold
authors.initials: A
authors.lastname: Felsenfeld
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Almaden
mesh_terms: D000818:Animals; D002117:Calcitriol / Q000378:metabolism; D002118:Calcium / Q000172:deficiency* / Q000378:metabolism* / Q000494:pharmacology; D002125:Calcium Gluconate / Q000494:pharmacology; D005346:Fibroblast Growth Factors / Q000097:blood* / Q000187:drug effects; D006996:Hypocalcemia / Q000378:metabolism*; D008297:Male; D023421:Models, Animal; D010281:Parathyroid Hormone / Q000378:metabolism; D016105:Parathyroidectomy; D016226:Phosphorus, Dietary / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D014807:Vitamin D / Q000378:metabolism
chemical_list: C505605:Fgf23 protein, rat; D010281:Parathyroid Hormone; D016226:Phosphorus, Dietary; D014807:Vitamin D; D005346:Fibroblast Growth Factors; D002117:Calcitriol; D002125:Calcium Gluconate; D002118:Calcium