A 34-year-old woman with Graves' disease is 8 weeks pregnant. She is currently on propylthiouracil. Thyroid function shows TSH <0.01, fT4 2.8 times upper limit. According to current endocrine guidelines, the preferred management in the second trimester of this patient is:

• A Continue PTU throughout pregnancy
• B Perform thyroidectomy immediately
• C Switch to methimazole in the second trimester ✓
• D Switch to radioactive iodine ablation

Explanation

PTU is preferred in the first trimester because methimazole is associated with aplasia cutis and choanal/esophageal atresia (embryopathy) during organogenesis. However, PTU carries risk of severe hepatotoxicity, so current ATA/Endocrine Society guidelines recommend switching from PTU to methimazole after the first trimester (weeks 14–16 onwards). RAI is absolutely contraindicated in pregnancy. Surgery is reserved for failed or intolerant drug therapy, preferably in the second trimester if unavoidable.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.