Phosphorus

Question 1

phosphorus function

Answer 1

formation of bones and teeth, CHO + fat metabolism, protein synthesis, cell/ tissue repair, ATP synthesis, phosphorylation of various B vitamin forms

Question 2

balance

Answer 2

intestinal absorption, kidney excretion, bone reservoir

PTH, V3, FGF23 regulates homeostasis

Question 3

control of serum levels – PTH

Answer 3

absorption
PTH mediated renal excretion, most Pi absorbed in proximal tubule
rate limiting, NaPi cotransporter type 2a in proximal tubule

Question 4

control of serum levels – FGF23

Answer 4

(-) transcription of NaPi cotransporter genes in proximal tubule –> inc Pi excretion

FGF23 (-) 1a hydroxylase, (+) 24 hydroxylase –> low calcitriol –> dec Pi absorption, inc Pi excretion inf kidneys

Question 5

hypophosphatemia

Answer 5

starvation refeeding inc Pi demand in cells. increased CHO –> inc insulin, inc glucose phosphorylation, dec ECF Pi

alcohol withdrawal. alcohol inhibits Pi absorption, malnourished

DKA (during treatment). inc insulin –> inc ICF glucose + Pi –> low ECF Pi