Renal: Gitelman syndrome: 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: Gitelman syndrome

Sample item

A 24-year-old woman has muscle cramps, hypokalaemic metabolic alkalosis, hypomagnesaemia, low urinary calcium excretion and a normal-to-low blood pressure. Which transporter is defective?

ASodium-potassium-2 chloride cotransporter of the thick ascending limbBEpithelial sodium channel of the collecting ductCThiazide-sensitive sodium chloride cotransporter of the distal convoluted tubuleDSodium-hydrogen exchanger of the proximal tubule

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

The answer and the reasoning

C. Thiazide-sensitive sodium chloride cotransporter of the distal convoluted tubule

Gitelman syndrome results from inactivating mutations of NCC (SLC12A3) and mimics chronic thiazide use. Salt wasting causes hypokalaemic alkalosis, and distal calcium reabsorption rises, giving hypocalciuria with magnesium wasting. Bartter syndrome, from NKCC2 defects, has hypercalciuria instead.

Option by option

A. Sodium-potassium-2 chloride cotransporter of the thick ascending limb
NKCC2 loss mimics loop diuretics and causes hypercalciuria.
B. Epithelial sodium channel of the collecting duct
Gain-of-function of ENaC in Liddle syndrome causes hypertension, not low pressure.
C. Thiazide-sensitive sodium chloride cotransporter of the distal convoluted tubule (correct)
Correct. NCC loss mimics a thiazide, producing hypocalciuria and hypomagnesaemia.
D. Sodium-hydrogen exchanger of the proximal tubule
A proximal sodium-hydrogen exchange defect would cause bicarbonate loss and acidosis.

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.

Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is C, Thiazide-sensitive sodium chloride cotransporter of the distal convoluted tubule. Gitelman syndrome results from inactivating mutations of NCC (SLC12A3) and mimics chronic thiazide use.

Why is "Sodium-potassium-2 chloride cotransporter of the thick ascending limb" not the answer?

NKCC2 loss mimics loop diuretics and causes hypercalciuria.

Why is "Epithelial sodium channel of the collecting duct" not the answer?

Gain-of-function of ENaC in Liddle syndrome causes hypertension, not low pressure.

Why is "Sodium-hydrogen exchanger of the proximal tubule" not the answer?

A proximal sodium-hydrogen exchange defect would cause bicarbonate loss and acidosis.

What concept does this question test?

It tests Renal: Gitelman syndrome in Physiology. Salt wasting causes hypokalaemic alkalosis, and distal calcium reabsorption rises, giving hypocalciuria with magnesium wasting. Bartter syndrome, from NKCC2 defects, has hypercalciuria instead.

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 Renal: Gitelman syndrome?

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.