Thyroid drugs: levothyroxine in pregnancy: practice question

A Pharmacology 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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Pharmacology · Thyroid drugs: levothyroxine in pregnancy

Sample item

A 28-year-old woman with primary hypothyroidism is stable on levothyroxine 100 micrograms daily. A pregnancy test is positive at 5 weeks. What is the appropriate change to her treatment?

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

The answer and the reasoning

C. Increase the levothyroxine dose by about 25 to 30% and monitor TSH every 4 weeks

Thyroid hormone requirement rises early in pregnancy because of increased thyroxine-binding globulin and placental changes, while the fetus depends on maternal thyroxine during the first trimester. The usual response is to raise the dose by about 25 to 30% as soon as pregnancy is confirmed, and to monitor TSH every four weeks in the first half. Untreated maternal hypothyroidism is linked to impaired fetal neurodevelopment.

Option by option

  • A. Continue the same dose until TSH rises in the third trimester

    Delaying the change would leave her hypothyroid during critical fetal brain development.

  • B. Replace levothyroxine with propylthiouracil

    Propylthiouracil is an antithyroid drug that would induce hypothyroidism.

  • C. Increase the levothyroxine dose by about 25 to 30% and monitor TSH every 4 weeks (correct)

    Dose is raised early to meet greater requirements and protect fetal neurodevelopment.

  • D. Stop levothyroxine to avoid fetal exposure

    Stopping levothyroxine would cause maternal hypothyroidism with fetal risk.

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 Pharmacology question

What is the answer to this Pharmacology question?

The best answer is C, Increase the levothyroxine dose by about 25 to 30% and monitor TSH every 4 weeks. Thyroid hormone requirement rises early in pregnancy because of increased thyroxine-binding globulin and placental changes, while the fetus depends on maternal thyroxine during the first trimester.

Why is "Continue the same dose until TSH rises in the third trimester" not the answer?

Delaying the change would leave her hypothyroid during critical fetal brain development.

Why is "Replace levothyroxine with propylthiouracil" not the answer?

Propylthiouracil is an antithyroid drug that would induce hypothyroidism.

Why is "Stop levothyroxine to avoid fetal exposure" not the answer?

Stopping levothyroxine would cause maternal hypothyroidism with fetal risk.

What concept does this question test?

It tests Thyroid drugs: levothyroxine in pregnancy in Pharmacology. The usual response is to raise the dose by about 25 to 30% as soon as pregnancy is confirmed, and to monitor TSH every four weeks in the first half. Untreated maternal hypothyroidism is linked to impaired fetal neurodevelopment.

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 drugs: levothyroxine in pregnancy?

Learn drugs as classes, then the exception in each class that an examiner would pick. Then use the flashcards and the other Pharmacology 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.