Calcium and Phosphorus in Chronic Renal Failure - USMLE Forums
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  #1  
Old 08-01-2011
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Kidney Calcium and Phosphorus in Chronic Renal Failure

In chronic renal failure we ve decreased vit D activation due to lack of alpha1 hydroxylase so we go into secondary hyperparathyriodism
What will be the changes in Calcium and phosphate??

a. both increase
b. Ca increases n phosphate decreases
c. both decrease
d. Ca decrease n phosphate increased
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Old 08-01-2011
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C: both increase
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  #3  
Old 08-01-2011
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D- Calcium decreases and phosphate increases.
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Old 08-01-2011
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d
Ca dec bcoz vit d absent nd PO4 inc bcoz kidneys unable to excrete it
plus PTH also inc
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Old 08-01-2011
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D) accumulation of phosphate decreases Ca.->>which increases Parathyroid fucntion to compensate Ca2+ decline
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Old 08-01-2011
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Ca down & P up
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Old 08-02-2011
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Ca decrease and Po4 increases

Ca decreased => Sec Hyperparathyroidism=> Kidney failed => Po4 increases => Product of PO4 and Ca is greater than solubility Product leading to bone deposition of Ca => Ca decreases
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Old 08-02-2011
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definitely d
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Old 08-02-2011
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well yes the rite ans is D but wanted to c more explanations

Last edited by qurat21; 08-02-2011 at 05:28 AM.
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Old 08-03-2011
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There are 3 main controllers of calcium concentration during chronic renal failure: acute, subacute and Chronic. Initially, due to the decrease in GFR, the concentration of phosphate in the plasma will increase which binds to calcium causing hypocalcemia. This will trigger the release of parathyroid hormone which will try to bring the calcium level up again and lower the phosphate level. Later the kidney fails to produce 1 alpha hydroxylase resulting in no vitamin D and thus hyocalcemia ensues. Phosphate level remains high despite the action of PTH because the GFR is decreased to the extent that it overrules the ability of PTH to excrete it. End result: low calcium and high phosphate levels. Hope this helps.
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  #11  
Old 08-03-2011
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defintely D is the ans for CRF but for hypovitaminosis D alone both of them dec.. but here the ans is D
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Old 09-30-2012
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As vit d is required to absorb both calcium and phosphorus it's lack will lead to decrease in both
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Old 09-30-2012
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know this:

All electrolytes increase in chronic renal failure except calcium ...

so D is the answer
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Old 09-30-2012
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i think the answer is B, coz PTH increases the ca level in blood while decreasing phosphorus.. we can also call it PTH(phosphorus trashing hormone).. any explanation guys?
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Old 09-30-2012
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Smile Ans is d

In chronic renal failure kidney cannot excrete po4 so leads to increase in po4..
As active form of vit D is not synthesized by diseased kidney,it severely affects the absorption of ca2+ from intestine...so It leads to secondary increase in PTH..eventhough it cannot replace enough Ca2+..so calcium level is low or taken as low normal....hence the Ans is low calcium and increased PO4...
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