Renal: calcium handling and thiazides: practice question

A Physiology 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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Physiology · Renal: calcium handling and thiazides

Sample item

A 40-year-old man with recurrent calcium oxalate stones and hypercalciuria is started on hydrochlorothiazide. How does the drug reduce urinary calcium?

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

The answer and the reasoning

A. Enhances calcium reabsorption in the distal convoluted tubule

Thiazides block the Na-Cl cotransporter, which lowers intracellular sodium in distal convoluted tubule cells. The basolateral Na-Ca exchanger then extrudes more calcium and apical calcium entry through TRPV5 rises, so urinary calcium falls. Loop diuretics have the opposite effect.

Option by option

  • A. Enhances calcium reabsorption in the distal convoluted tubule (correct)

    Correct. Distal tubular calcium reabsorption is increased, giving hypocalciuria.

  • B. Reduces calcium filtration at the glomerulus

    Filtration is not reduced; calcium excretion is lowered by tubular handling.

  • C. Increases calcium reabsorption in the thick ascending limb

    Reabsorption in the thick ascending limb is reduced by loop diuretics, increasing calciuria.

  • D. Inhibits parathyroid hormone release

    PTH release is not inhibited by thiazides, which may even raise serum calcium.

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 Physiology question

What is the answer to this Physiology question?

The best answer is A, Enhances calcium reabsorption in the distal convoluted tubule. Thiazides block the Na-Cl cotransporter, which lowers intracellular sodium in distal convoluted tubule cells.

Why is "Reduces calcium filtration at the glomerulus" not the answer?

Filtration is not reduced; calcium excretion is lowered by tubular handling.

Why is "Increases calcium reabsorption in the thick ascending limb" not the answer?

Reabsorption in the thick ascending limb is reduced by loop diuretics, increasing calciuria.

Why is "Inhibits parathyroid hormone release" not the answer?

PTH release is not inhibited by thiazides, which may even raise serum calcium.

What concept does this question test?

It tests Renal: calcium handling and thiazides in Physiology. The basolateral Na-Ca exchanger then extrudes more calcium and apical calcium entry through TRPV5 rises, so urinary calcium falls. Loop diuretics have the opposite effect.

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 Renal: calcium handling and thiazides?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology 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.