NBME 18 Intestinal calcium absorption (NBME Answers)

Retired NBME 18 Answers

nbme18/Block 4/Question#30 (reveal difficulty score)
5 yo girl, 1 day severe leg pain after ...
Intestinal calcium absorption 🔍 / 📺 / 🌳 / 📖
tags: GI

+4 upvote downvote
submitted by staph_aureusxx(9)

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So the vitamin deficiency the girl is having is vitamin D. why? because of her diet how? bone fractures + demographics result? diet --> gut fiercely affects intestinal calcium absorption in the gut.

the distractor was the bone fractures and poor wound healing which wanted you to pick collagen synthesis.. which I did twice -_-.. but I think in this case of a question; when it seems too simple; explain to yourself why the other answers don't make sense.

I think I keep choosing A not realizing that vitamin C deficiency would present with lot more signs and symptoms like easy bruising and bleeding gums.

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pg32 I think it's also important to realize that their veganism is the giveaway. Vitamin C is in fruits and vegetables and wouldn't be lacking in her diet. Vitamin D3 is mostly found in milk supplemented with Vitamin D, though it can be found in smaller amounts in plants as well. +6

pg32 Additionally, if you want to get reeeeally picky about collagen synthesis as an answer choice (cuz I was debating picking that one as well), a vitamin C deficiency causes an issue with collagen cross-linking rather than "synthesis." I know it is nit-picky, but the question says the vitamin deficiency DIRECTLY affects the process. +1

dave_ https://www.youtube.com/watch?v=e_vFCmv9KZ4 +1

blah I nearly went with something to do with collagen synthesis, but what changed my mind was that it said that they did not give the patient ANY dairy products. +

stunna216 FA has a whole chapter on parts of the world with very little sun, so that's why Greenland should have been a dead giveaway for ↓Vit D. common knowledge +

stunna216 Iceland** +

heenaasnani @pg32 I think copper is needed for cross linking of collagen, whereas Vitamin C is needed for hydroxylation of proline and lysine which is a part of collagen synthesis. +

plaguedbyspleen Vegan diet, bone pain, fractures. Don't think too much about it - this is osteomalacia/rickets. You could also question how much sun she was getting in Iceland. +

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submitted by ∗mamed(25)

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Was anyone thinking about answer choice E- PTH hormone production? I was in between a Vitamin D and Calcium deficiency with the no milk. I ended up going with vitamin D (thank you sketchy) but couldn't rule out a calcium deficiency in my mind.

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+1 upvote downvote
submitted by ∗chadgas(2)

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Did anyone have any difficulty deciding between C and E? I knew it was a Vitamin D deficiency, but doesn't calcitriol feedback to decrease PTH production?

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nbmeanswersownersucks I think it is because the question stem asks about the deficiency that "DIRECTLY" affects a process. Vitamin D directly affects calcium reabsorption whereas it is the rise in Calcium (caused by Vitamin D) that then negatively regulates PTH production (so Vitamin D indirectly regulates PTH). The "directly" wording has gotten the best of me more than a few times so now I've become hyper-aware of that wording. +3

nbmeanssux Also, I just realized it asks about "vitamin deficiency" and calcium is technically a mineral :/ +

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