CKD-bone and mineral dz Flashcards
what are the effects of PTH?
increase bone resorption, increase conversion of 25OH-D to 2,25OH-D and thus increase intestinal Ca absorption
how does hypoalbuminemia affect ionize Ca conc?
it increases it b/c normally Ca is bound to albumin
what are the three major hormones regulating Pi?
vit. D, PTH, FGF23
Two methods of intestinal Pi uptake
passive (via Npt2b transporters) and active (stimulated by calcitriol)
Calcitriol
active metabolite of Vit. D. Stimulates active Ca (major factor) and Pi (minor factor) absorption.
factors that increase Pi excretion
Increased plasma conc, FGF23, PTH all cause endocytosis of transporter
FGF23: where produced. 3 actions
osteocytes in response to phosphate load. Inhibits renal 1,a-hydroxylase to decrease calcitriol, ^renal excretion, inhibit PTH
What channel does majority of Pi regulation and where?
Npt2b Na-P cotransporter in PT. Type 2a in apical membrane
Three effects of PTH
stimulates 1,a-hydroxylase to ^calcitriol; renal P excretion; ^serum Ca by bone resorption and renal reabsorption
principle regulator of Mg urine conc
Plasma Mg conc.. Most reabsorpt is paracellular in TAL
what is the problem in Familial Hypocalciuric Hypercalcemia Vs Hyperparathyroidism
hypercalcemia is not sensed (CaR mutation). PTH slightly elevated; Both CaR alleles mutated. more severe hypercalcemia and PTH elevation
what constitutes vit d deficiency
Serum 25(OH)D<30
what are the high and low turnover bone diseases
Osteitis Fibrosa (HyperPTH), Adynamic bone osteomalacia (Ca, Calcitriol, D analogs)
How do PTH, Ca, P change with decreasing GFR
PTH goes up but Ca and P stay constant until very low GFR then P rises
three principle hormonal changes in CKD
calcitriol down, FGF and PTH up
