vitamin d toxicity

[pezzang]

Why does vitamin d toxicity result in normal alk phos? Shouldn't it be raised because of the increased bone resorption?

Also, in renal failure, why is the alk phos again remain normal?
Shouldn't it again rise b/c Renal failure-> low active vit D-> low ca->pth rises->increase alk phos?



I thought I knew endocrine pretty well but oh well..

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[SmokD]

If I remember correctly Alk phos is an indicator of osteoblast activity, not osteoclast. Correct me if I'm wrong.

 

[Sheldor]

If I remember correctly Alk phos is an indicator of osteoblast activity, not osteoclast. Correct me if I'm wrong.

Thats what I have annotated into my First Aid from Uworld.

 

[da8s0859q]

If I remember correctly Alk phos is an indicator of osteoblast activity, not osteoclast. Correct me if I'm wrong.

Yeah. I learned it as ALP for osteoblasts, urinary hydroxyproline for osteoclasts.

Why does vitamin d toxicity result in normal alk phos? Shouldn't it be raised because of the increased bone resorption?

Also, in renal failure, why is the alk phos again remain normal?
Shouldn't it again rise b/c Renal failure-> low active vit D-> low ca->pth rises->increase alk phos?

I thought I knew endocrine pretty well but oh well..

Someone's gonna have to fact-check me, but in CKD, it's an issue of 2° hyperparathyroidism -- in which case, ALP should be increased. The only way I remember this is by remembering that PTH acts on osteoBLASTS, which then signal osteoclasts to do their thing -- but the direct effect is actually on osteoblasts themselves. Pretty lousy way to remember it since PTH certainly doesn't induce osteoid secretion though.

Urinary hydroxyproline as a measure of osteoclast breakdown of bone should also be increased, I'd think. It's not too recent, but this seems to back that up.

 

[ArcGurren]

For the record Vit D toxicity is really, really hard to acquire if I recall correctly. The main vitamin toxicity (which came up on my exam) is Vit A tox, because it can actually be fatal.

 

[tco]

For the record Vit D toxicity is really, really hard to acquire if I recall correctly. The main vitamin toxicity (which came up on my exam) is Vit A tox, because it can actually be fatal.

Always helpful to know if you're ever hunting polar bear.

Does anyone actually know why it's fatal? Liver failure?

 

[ArcGurren]

Always helpful to know if you're ever hunting polar bear.

Does anyone actually know why it's fatal? Liver failure?

It's extremely toxic and causes problems with cell proliferation - you see a lot of cutaneous manifestations as a result. I don't know the exact reasoning (though to be fair I've purged my brain of a lot of this post-exam) but the toxicity is incredibly severe and actually systemic.