hypercalecmia causes bone demineralization?

[cheruka]

Hi,
The qbank I am doing mentions hypercalcemia as one of the complications of vit D toxicity. That, I understand. But it also says it causes bone demineralization. Why would that be? I mean, if there is too much calcium in the blood, calcitonin should get released and PTH shoudl get suppressed, correct?

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[zstranger2]

Hi,
The qbank I am doing mentions hypercalcemia as one of the complications of vit D toxicity. That, I understand. But it also says it causes bone demineralization. Why would that be? I mean, if there is too much calcium in the blood, calcitonin should get released and PTH shoudl get suppressed, correct?

It is possible, it depends on the scenario. Is the kidney working fine? If the kidney is not working, then the vit. D toxicity is probably not the direct reason for the hypercalcemia. It could be hyperparathyroidism secondary to CKD, where the kidney is not responding to the effects of the parathyroid hormone. In that situation, the parathyroid hormone continues to act as if there was 'hypocalcemia', resulting in more hypercalcemia and demineralization.

What did the question say exactly?

 

[Transposony]

Vit D causes rise in phosphate levels by two mechanisms:
1. By increased intestinal absorption
2. By release of phosphate from the bone-->>demineralization.

Also, high phosphate will stimulate PTH