Endocrinology: hypothyroidism in pregnancy: practice question

A General Medicine 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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General Medicine · Endocrinology: hypothyroidism in pregnancy

Sample item

A 28-year-old woman with primary hypothyroidism on a stable dose of levothyroxine has a positive home pregnancy test. What should be done?

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

The answer and the reasoning

D. Increase the levothyroxine dose by about 25 to 30% and check TSH regularly

Thyroxine requirements rise by about 25 to 50% in pregnancy because of raised thyroxine-binding globulin from oestrogen and increased demand. The foetus depends on maternal thyroxine in the first trimester for neurodevelopment, so the dose is increased promptly on confirmation of pregnancy and monitored every 4 weeks, with a TSH target in the lower half of the trimester range.

Option by option

  • A. Switch to liothyronine

    Liothyronine does not cross the placenta adequately and is not recommended in pregnancy.

  • B. Continue the same dose until the TSH becomes abnormal

    Waiting for an abnormal TSH leaves the foetus exposed to deficiency during early brain development.

  • C. Stop levothyroxine until the second trimester

    Stopping therapy would cause overt hypothyroidism and risk miscarriage and impaired foetal brain development.

  • D. Increase the levothyroxine dose by about 25 to 30% and check TSH regularly (correct)

    An early empirical dose increase prevents maternal hypothyroidism and protects foetal neurodevelopment.

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 General Medicine question

What is the answer to this General Medicine question?

The best answer is D, Increase the levothyroxine dose by about 25 to 30% and check TSH regularly. Thyroxine requirements rise by about 25 to 50% in pregnancy because of raised thyroxine-binding globulin from oestrogen and increased demand.

Why is "Switch to liothyronine" not the answer?

Liothyronine does not cross the placenta adequately and is not recommended in pregnancy.

Why is "Continue the same dose until the TSH becomes abnormal" not the answer?

Waiting for an abnormal TSH leaves the foetus exposed to deficiency during early brain development.

Why is "Stop levothyroxine until the second trimester" not the answer?

Stopping therapy would cause overt hypothyroidism and risk miscarriage and impaired foetal brain development.

What concept does this question test?

It tests Endocrinology: hypothyroidism in pregnancy in General Medicine. The foetus depends on maternal thyroxine in the first trimester for neurodevelopment, so the dose is increased promptly on confirmation of pregnancy and monitored every 4 weeks, with a TSH target in the lower half of the trimester range.

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 Endocrinology: hypothyroidism in pregnancy?

For each disease know the classic presentation, the best test, and the first-line treatment. Then use the flashcards and the other General Medicine 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.