A 10-day-old neonate presents with irritability, tachycardia (HR 185/min), poor weight gain, and mild exophthalmos. The mother has a history of Graves disease treated with radioactive iodine ablation 3 years ago and is currently on levothyroxine. TSH is <0.01 mIU/L and free T4 is 5.2 ng/dL. What is the most likely mechanism?
- A Neonatal autoimmune thyroiditis activating TSH receptors
- B Transplacental transfer of maternal thyroxine
- C Transplacental transfer of TSH receptor stimulating antibodies ✓
- D Congenital TSH receptor activating mutation
Correct answer: C. Transplacental transfer of TSH receptor stimulating antibodies
Explanation
Neonatal Graves disease results from transplacental passage of maternal TSH receptor stimulating immunoglobulins (TRAb). It occurs in 1-5% of infants born to mothers with current or past Graves disease, as antibodies may persist despite ablation. The condition is self-limiting as maternal antibodies clear over 2-3 months.
Reference: Williams Textbook of Endocrinology, 14th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.