Clinical biochemistry: thyroxine-binding globulin in pregnancy: 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: thyroxine-binding globulin in pregnancy

Sample item

A healthy pregnant woman at 20 weeks has no symptoms, a normal TSH and free T4, but total T4 is much higher than the non-pregnant range. What explains this?

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

The answer and the reasoning

D. Oestrogen-induced rise in thyroxine-binding globulin

Oestrogen raises hepatic synthesis and sialylation of thyroxine-binding globulin, so total T4 and T3 rise while free hormone and TSH stay normal. Free hormone and TSH therefore guide diagnosis in pregnancy. No treatment is needed.

Option by option

  • A. Graves disease

    Graves disease would suppress TSH and raise free T4.

  • B. Subclinical thyrotoxicosis from hCG

    hCG-mediated thyroid stimulation would lower TSH.

  • C. Resistance to thyroid hormone

    Hormone resistance would raise free T4 with a non-suppressed TSH.

  • D. Oestrogen-induced rise in thyroxine-binding globulin (correct)

    Correct. More binding protein raises total hormone without changing the free level.

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 D, Oestrogen-induced rise in thyroxine-binding globulin. Oestrogen raises hepatic synthesis and sialylation of thyroxine-binding globulin, so total T4 and T3 rise while free hormone and TSH stay normal.

Why is "Graves disease" not the answer?

Graves disease would suppress TSH and raise free T4.

Why is "Subclinical thyrotoxicosis from hCG" not the answer?

hCG-mediated thyroid stimulation would lower TSH.

Why is "Resistance to thyroid hormone" not the answer?

Hormone resistance would raise free T4 with a non-suppressed TSH.

What concept does this question test?

It tests Clinical biochemistry: thyroxine-binding globulin in pregnancy in Biochemistry. Free hormone and TSH therefore guide diagnosis in pregnancy. No treatment is needed.

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: thyroxine-binding globulin in pregnancy?

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.