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Physiologic jaundice — USMLE Step 3 MCQ

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HardPediatrics (well-child, chronic management)Physiologic jaundiceUSMLE Step 3

Newborn screening shows TSH 68 mIU/L and low thyroxine in an asymptomatic 6-day-old infant. What is the best next step?

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Correct answer: B — Confirm serum thyroid tests and begin levothyroxine now

The best answer is “Confirm serum thyroid tests and begin levothyroxine now”. Neurodevelopment depends on rapid thyroid-hormone replacement. Confirmatory serum testing is obtained urgently, but treatment should not be delayed when screening strongly indicates primary congenital hypothyroidism. Abnormal newborn screening requires prompt confirmation and levothyroxine without avoidable delay.

Reference: NCBI Bookshelf: Congenital Hypothyroidism: https://www.ncbi.nlm.nih.gov/books/NBK558913/