Endocrine drugs: active vitamin D in kidney disease: practice question

A Pharmacology 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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Pharmacology · Endocrine drugs: active vitamin D in kidney disease

Sample item

A 55-year-old man with stage 5 chronic kidney disease has low calcium, high phosphate and high PTH. Despite adequate cholecalciferol, his 1,25-dihydroxyvitamin D is low. Which supplement is appropriate?

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

The answer and the reasoning

C. Calcitriol

In advanced kidney disease the renal 1-alpha-hydroxylase is lost, so native vitamin D cannot be activated. Calcitriol or analogues bypass this step, though serum calcium and phosphate must be monitored to avoid hypercalcaemia.

Option by option

  • A. Cholecalciferol in higher doses

    Cholecalciferol still needs renal 1-alpha-hydroxylation.

  • B. Calcitonin

    Calcitonin lowers calcium and is not a replacement for active vitamin D.

  • C. Calcitriol (correct)

    Correct. Calcitriol is already hydroxylated and does not need renal activation.

  • D. Ergocalciferol in higher doses

    Ergocalciferol still needs renal activation, so more of it will not help.

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 Pharmacology question

What is the answer to this Pharmacology question?

The best answer is C, Calcitriol. In advanced kidney disease the renal 1-alpha-hydroxylase is lost, so native vitamin D cannot be activated.

Why is "Cholecalciferol in higher doses" not the answer?

Cholecalciferol still needs renal 1-alpha-hydroxylation.

Why is "Calcitonin" not the answer?

Calcitonin lowers calcium and is not a replacement for active vitamin D.

Why is "Ergocalciferol in higher doses" not the answer?

Ergocalciferol still needs renal activation, so more of it will not help.

What concept does this question test?

It tests Endocrine drugs: active vitamin D in kidney disease in Pharmacology. Calcitriol or analogues bypass this step, though serum calcium and phosphate must be monitored to avoid hypercalcaemia.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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 Endocrine drugs: active vitamin D in kidney disease?

Learn drugs as classes, then the exception in each class that an examiner would pick. Then use the flashcards and the other Pharmacology 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.