A 2-day-old neonate born to a mother with Graves disease (on propylthiouracil during pregnancy) presents with tachycardia (210/min), irritability, poor weight gain, and a small diffuse goiter. TSH is undetectable and free T4 is markedly elevated. What is the definitive underlying cause?
- A Neonatal thyrotropin receptor activating mutation
- B Propylthiouracil withdrawal effect
- C Transplacental passage of maternal TSH-receptor stimulating antibodies (TRAb) ✓
- D Congenital TSH-secreting pituitary adenoma
Correct answer: C. Transplacental passage of maternal TSH-receptor stimulating antibodies (TRAb)
Explanation
Neonatal Graves disease results from transplacental transfer of maternal TSH-receptor stimulating immunoglobulins (TRAb). It presents within the first days of life with tachycardia, goiter, and hyperthyroidism, and is self-limiting as maternal antibodies clear over weeks to months. Propylthiouracil withdrawal does not cause neonatal thyrotoxicosis. C germline activating TSH-receptor mutation (non-autoimmune hyperthyroidism) is rare and independent of maternal Graves. TSH-secreting adenoma would show elevated, not suppressed, TSH.
Reference: Williams Textbook of Endocrinology, 14th ed.
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