Vitamin D

[empirestate114]

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Vitamin D is used to maintain blood calcium levels so ideally it shud have a Bone resorption action on bones but in First aid errata it mentions It causes bone mineralisation which is also true if u see its deficency causes rickets and osteomalacia !!!


so what is it Bone mineralisation Or Bone resorption !!!!!!!!!!!!!!!!!!!!!!!

plz help

 

[Phloston]

It's both.

Vitamin D increases the number of calcium-binding receptors on the apical enterocytes, in addition to increasing phosphate reabsorption. This causes the serum concentrations of calcium and phosphate to exceed their solubility product, thereby triggering a decrease in PTH and, further, bone deposition.

However, with hypervitaminosis-D, an increased number of vitamin D molecules will bind to osteoblastic intracytoplasmic steroid receptors, thereby inducing transcription of RANK-L and M-CSF, causing bone resorption.

Therefore, the indirect effects of vitamin D, as well as those at physiologic levels, favor bone deposition, whereas those concomitant to hypervitaminosis induce resorption.

Hope that helps,

 

[Ronin786]

BRS Physio mentions that Vitamin D causes bone resorption in normal concentrations, but the difference here is that this is resorption of old bone. So it'll take out the old and bring in the new via mineralisation.

 

[Phloston]

To anyone viewing this thread, it's worth your 20 seconds to look at this:

It's p. 441 from the 2002 Kaplan lecture notes.