Thyroid hormone synthesis: thyroid peroxidase: 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.

Try it

Biochemistry · Thyroid hormone synthesis: thyroid peroxidase

Sample item

A woman with a firm goitre has lymphocytic infiltration and Hurthle cells on biopsy. Her serum contains autoantibodies once called antimicrosomal. Which enzyme do they target?

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

The answer and the reasoning

D. Thyroid peroxidase

The antibodies formerly called antimicrosomal are directed at the follicular cell enzyme and are the most sensitive marker of Hashimoto thyroiditis. Anti-thyroglobulin antibodies are also common. Anti-21-hydroxylase and anti-GAD antibodies belong to other autoimmune endocrine diseases.

Option by option

  • A. Glutamic acid decarboxylase

    Glutamic acid decarboxylase is the autoantigen in type 1 diabetes.

  • B. 21-Hydroxylase

    21-Hydroxylase is the autoantigen in autoimmune adrenalitis.

  • C. Iodothyronine deiodinase

    Deiodinase is not the classic autoantigen in Hashimoto thyroiditis.

  • D. Thyroid peroxidase (correct)

    Correct. The antibodies target the peroxidase and mark Hashimoto thyroiditis.

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.

More Biochemistry questions

Questions about this Biochemistry question

What is the answer to this Biochemistry question?

The best answer is D, Thyroid peroxidase. The antibodies formerly called antimicrosomal are directed at the follicular cell enzyme and are the most sensitive marker of Hashimoto thyroiditis.

Why is "Glutamic acid decarboxylase" not the answer?

Glutamic acid decarboxylase is the autoantigen in type 1 diabetes.

Why is "21-Hydroxylase" not the answer?

21-Hydroxylase is the autoantigen in autoimmune adrenalitis.

Why is "Iodothyronine deiodinase" not the answer?

Deiodinase is not the classic autoantigen in Hashimoto thyroiditis.

What concept does this question test?

It tests Thyroid hormone synthesis: thyroid peroxidase in Biochemistry. Anti-thyroglobulin antibodies are also common. Anti-21-hydroxylase and anti-GAD antibodies belong to other autoimmune endocrine diseases.

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 Thyroid hormone synthesis: thyroid peroxidase?

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.