Vitamins and minerals: Pendred syndrome: practice question

A Biochemistry 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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Biochemistry · Vitamins and minerals: Pendred syndrome

Sample item

A child has congenital sensorineural deafness and a goitre but remains euthyroid with normal thyroid hormone levels. Inner ear imaging shows an enlarged vestibular aqueduct. A defect in which protein is most likely?

ASodium-iodide symporter on the basolateral membraneBPendrin, an apical iodide-chloride transporterCThyroid peroxidaseDThyroglobulin

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

The answer and the reasoning

B. Pendrin, an apical iodide-chloride transporter

Pendred syndrome results from mutations in SLC26A4, encoding pendrin, which exports iodide across the apical membrane of thyrocytes and has a role in the inner ear. The result is deafness with goitre, usually with preserved thyroid function. Dyshormonogenetic goitres from other proteins do not cause deafness.

Option by option

A. Sodium-iodide symporter on the basolateral membrane
Symporter defects cause congenital hypothyroidism with low iodide uptake and no deafness.
B. Pendrin, an apical iodide-chloride transporter (correct)
Correct. Pendrin mutations link goitre to sensorineural deafness.
C. Thyroid peroxidase
A peroxidase defect gives dyshormonogenetic goitre with hypothyroidism but not deafness.
D. Thyroglobulin
A thyroglobulin defect gives goitre with hypothyroidism and low serum thyroglobulin, not deafness.

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 Biochemistry question

What is the answer to this Biochemistry question?

The best answer is B, Pendrin, an apical iodide-chloride transporter. Pendred syndrome results from mutations in SLC26A4, encoding pendrin, which exports iodide across the apical membrane of thyrocytes and has a role in the inner ear.

Why is "Sodium-iodide symporter on the basolateral membrane" not the answer?

Symporter defects cause congenital hypothyroidism with low iodide uptake and no deafness.

Why is "Thyroid peroxidase" not the answer?

A peroxidase defect gives dyshormonogenetic goitre with hypothyroidism but not deafness.

Why is "Thyroglobulin" not the answer?

A thyroglobulin defect gives goitre with hypothyroidism and low serum thyroglobulin, not deafness.

What concept does this question test?

It tests Vitamins and minerals: Pendred syndrome in Biochemistry. The result is deafness with goitre, usually with preserved thyroid function. Dyshormonogenetic goitres from other proteins do not cause deafness.

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 Vitamins and minerals: Pendred syndrome?

Build one table of enzyme deficiency, disease, inheritance and key finding, then revise it by spaced recall. Then use the flashcards and the other Biochemistry 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.