Nutrition and malnutrition: assessing vitamin D status: practice question

A Pediatrics question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Pediatrics · Nutrition and malnutrition: assessing vitamin D status

Sample item

An infant given large repeated doses of vitamin D has vomiting, constipation, polyuria and a high serum calcium. Which test best reflects the vitamin D status?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. Serum 25-hydroxyvitamin D

Serum 25-hydroxyvitamin D is the major circulating form and the best measure of vitamin D stores, and it is markedly raised in toxicity. Active 1,25-dihydroxyvitamin D is tightly regulated and may be normal or even low, so it is a poor guide.

Option by option

  • A. Urinary calcium excretion

    Urinary calcium is raised in hypercalcaemia, but it does not measure the vitamin level.

  • B. Serum 1,25-dihydroxyvitamin D

    The active form is regulated by calcium and PTH and is unreliable for stores.

  • C. Serum 25-hydroxyvitamin D (correct)

    Correct. The 25-hydroxy form reflects total stores and rises in toxicity.

  • D. Serum parathyroid hormone

    PTH is suppressed in hypercalcaemia, but it does not measure vitamin D status.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Pediatrics question

What is the answer to this Pediatrics question?

The best answer is C, Serum 25-hydroxyvitamin D. Serum 25-hydroxyvitamin D is the major circulating form and the best measure of vitamin D stores, and it is markedly raised in toxicity.

Why is "Urinary calcium excretion" not the answer?

Urinary calcium is raised in hypercalcaemia, but it does not measure the vitamin level.

Why is "Serum 1,25-dihydroxyvitamin D" not the answer?

The active form is regulated by calcium and PTH and is unreliable for stores.

Why is "Serum parathyroid hormone" not the answer?

PTH is suppressed in hypercalcaemia, but it does not measure vitamin D status.

What concept does this question test?

It tests Nutrition and malnutrition: assessing vitamin D status in Pediatrics. Active 1,25-dihydroxyvitamin D is tightly regulated and may be normal or even low, so it is a poor guide.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Nutrition and malnutrition: assessing vitamin D status?

Memorise milestones and the vaccine schedule as tables and revise them often. Then use the flashcards and the other Pediatrics questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.