低リン血症

Hypophosphatemia

健常成人においては，通常，血清リン値は2.5～4.5mg/dl程度に維持されている．小児の血清リン値は成人よりも高い．低リン血症は，①腸管からのリン吸収の低下，②腎臓からのリン喪失，③細胞内へのリンの移動により生じる．腎臓からのリン喪失は，Fanconi症候群や種々の遺伝性低リン血症性くる病，腫瘍随伴性低リン血症性骨軟化症など，様々な病態に伴う．低リン血症の中には，線維芽細胞増殖因子23(FGF23)の作用の過剰に基づく病態がいくつか存在し，FGF23の測定は低リン血症の鑑別診断において有用である．

In healthy adults, serum levels of inorganic phosphate is maintained about 2.5-4.5 mg/dl.　In children, serum levels of inorganic phosphate are higher than those in adults.　Hypophosphatemia is caused by 1) decreased absorption in the intestine, 2) increased renal excretion, or 3) translocation into the cells of phosphate.　Hypophosphatemia caused by increased renal excretion of phosphate is associated with various conditions, including Fanconi syndrome, hereditary hypophosphatemic rickets and tumor-induced hypophosphatemic osteomalacia.　Some of these hypophosphatemic conditions are caused by the increased action of a phosphaturic factor, fibroblast growth factor 23 (FGF23).　Measurement of serum levels of FGF23 is useful to make a differential diagnosis in hypophosphatemia.