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Old 07-28-2010
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Kidney Why not Hypocalciuria in Hyperparathyroidism!

How is the mechanism of hyperparathyroidism leading to hypercalcuria?

As I know, PTH will cause increased reabsorption of calcium within DCT. Logically, it should cause hypocalciuria if there is excess PTH.

Is it because of severe calcium overload that causes it to be hypercalciuric despite having increased calcium reabsorption? In this case, hypercalciuria should only happen in long-standing hyperPTH, shouldn't it?

Thanks in advance.
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Old 07-28-2010
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U know ... filterer load = GFR * amount / volume in plasma ... it means more calcium in plasma means more filtered load ... but amount of tranporter is limited .. which is transport maximum ... so due to much more filter load .. there is much more calcium in tubule but even tho high PTH there is limited transporter ... so remaining high amount of calcium excrete thru urine ....
This 24 hours urine calcium excretion differentiate Increase PTH due to familial hypercalcemic hypocalciuria and hypercalcemic hypercalciuria .....
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Old 07-28-2010
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Quote:
Originally Posted by FSUSTC View Post
U know ... filterer load = GFR * amount / volume in plasma ... it means more calcium in plasma means more filtered load ... but amount of tranporter is limited .. which is transport maximum ... so due to much more filter load .. there is much more calcium in tubule but even tho high PTH there is limited transporter ... so remaining high amount of calcium excrete thru urine ....
This 24 hours urine calcium excretion differentiate Increase PTH due to familial hypercalcemic hypocalciuria and hypercalcemic hypercalciuria .....
Thanks. You have explained it very well. Appreciated.
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Old 07-31-2010
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Quote:
Originally Posted by FSUSTC View Post
U know ... filterer load = GFR * amount / volume in plasma ... it means more calcium in plasma means more filtered load ... but amount of tranporter is limited .. which is transport maximum ... so due to much more filter load .. there is much more calcium in tubule but even tho high PTH there is limited transporter ... so remaining high amount of calcium excrete thru urine ....
This 24 hours urine calcium excretion differentiate Increase PTH due to familial hypercalcemic hypocalciuria and hypercalcemic hypercalciuria .....
Yep I was about to say something like this, simply if you have hyperparathyriodism you have a lot of Ca++ in the blood so all this Ca++ is spilled over in the urine.
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