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in primary hyperparathyroidism there is increased plasma Ca n decreased plasma phosphate...what happens to the solubility product here?..also there is increase in serum alkaline phosphatase which is an index of bone demeneralization n remodelling....does that mean that there is demineralization of bone here....??


Good question.Solubiliy product=[ca]X[po4]; so I think if we increase [ca] and decrease [phosphate] the solubility product would not change much logically, right?
Any comments?


PTH has receptor on osteoblasts..There is less Ca in body thats y there is hyperparathyrodisim to increase Ca levels...It promtoes osteoclastic resorption and demineralization of bone......PTH increases secretion of Vit D by enzyme 1 alpha hydroxylase..Vit D also has receptor on osteoblasts and it treleases alkaline phosphatases...
As Dr Golgan says PTH functions in maintaining Ca concentrations and Vit D plays role in mineralization


Yes hope4dabest everything you said is correct.But what happens to soulibility product in the case of increase of PTH?increase?decrease?or remains the same?


yunuz i too think that solubility product should remain the same logically...but demineralization takes place when the solubility product cannot think of a explanation for thisshaking head

hope4dabest...yes what u have said is right...i am just looking for a explanation according to the solubility product...

anyone plzconfused


in hyperparathyroidism the PTH causes a decrease in the plasma phosphate & increase in the ca levels, this is by the following mechanisms:
PTH stimulate the osteoblast, that causes the lay down of the bone & as there is a communication between it & the osteoclast also these later cells will be stimulated & causes resorption of the ca & phosphate from the bone but, the phosphate level will be decreased in the plasma cuz the PTH inhibit its reabsorption in the PCT, so this decrease in the phosphate level also further stimulate the resorption process,as the product of conc. will be lower than the solubility product , we can confirm that by the following:-
in the Kaplan book at the paragraph of relationship between ca & phosphate it says
(a decrease in the ca OR phosphate this leads to resorption of the bone) this is due to decrease in their product of conc. below the solubility product, then it said also in the kaplan book(For example a decrease in the phospate level alone would promote bone demineralizatioin) also this due to a decraese in their product of conc. below solubility product, in the hyperparathyroidism there is decrease in the phosphate level, also there is a secretion of the ca cuz its filtered load greater than the maximum threshold of the kidney so although there is an increase in the ca level in the plasma, it does not mean that it is tregulated( the concentration product to be regulated).
Finally it is more logically to say it is a DECREASED THEIR PRODUCT OF CONC. BELOW SOLUBILITY PRODUCT.nod

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