Clinical biochemistry: thyroid function tests: 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 · Clinical biochemistry: thyroid function tests

Sample item

A 38-year-old woman has fatigue and mild constipation. TSH is 12 mIU/L with normal free T4 and free T3 on two occasions. Which interpretation is correct?

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

The answer and the reasoning

A. Subclinical primary hypothyroidism

A raised TSH with normal free thyroid hormones defines subclinical primary hypothyroidism: the pituitary drives a failing gland to keep hormone levels normal. Overt hypothyroidism needs a low free T4. Central hypothyroidism gives a low or inappropriately normal TSH with low free T4. Anti-thyroid peroxidase antibodies predict progression, and treatment is considered with symptoms, a high TSH or antibodies.

Option by option

  • A. Subclinical primary hypothyroidism (correct)

    Correct. High TSH with normal free T4 is subclinical hypothyroidism.

  • B. Overt primary hypothyroidism

    Overt hypothyroidism requires a low free T4, which is normal here.

  • C. Sick euthyroid syndrome

    Sick euthyroid syndrome typically occurs in acute illness with low T3 and a low or normal TSH.

  • D. Central hypothyroidism

    Central hypothyroidism would show a low or normal TSH, not a high TSH.

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 Biochemistry question

What is the answer to this Biochemistry question?

The best answer is A, Subclinical primary hypothyroidism. A raised TSH with normal free thyroid hormones defines subclinical primary hypothyroidism: the pituitary drives a failing gland to keep hormone levels normal.

Why is "Overt primary hypothyroidism" not the answer?

Overt hypothyroidism requires a low free T4, which is normal here.

Why is "Sick euthyroid syndrome" not the answer?

Sick euthyroid syndrome typically occurs in acute illness with low T3 and a low or normal TSH.

Why is "Central hypothyroidism" not the answer?

Central hypothyroidism would show a low or normal TSH, not a high TSH.

What concept does this question test?

It tests Clinical biochemistry: thyroid function tests in Biochemistry. Overt hypothyroidism needs a low free T4. Central hypothyroidism gives a low or inappropriately normal TSH with low free T4. Anti-thyroid peroxidase antibodies predict progression, and treatment is considered with symptoms, a high TSH or antibodies.

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 Clinical biochemistry: thyroid function tests?

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.