A 10-day-old neonate has tachycardia (HR 190/min), marked irritability, poor weight gain despite good feeds, a small goitre, and warm moist skin. The mother had Graves disease treated with radioiodine two years ago. What is the underlying mechanism of this presentation?
- A Transplacental passage of TSH receptor-stimulating immunoglobulins ✓
- B Excess transfer of maternal thionamide drug through breast milk
- C Activating germline mutation of the TSH receptor gene
- D Maternal antibody-mediated destruction of the fetal thyroid
Correct answer: A. Transplacental passage of TSH receptor-stimulating immunoglobulins
Explanation
Neonatal thyrotoxicosis results from transplacental transfer of maternal TSH receptor-stimulating IgG antibodies; it occurs even after maternal radioiodine or surgery because the antibodies persist. It is self-limited over weeks as maternal IgG decays, managed with antithyroid drugs plus a beta blocker. Maternal thionamides crossing the placenta or breast milk cause neonatal hypothyroidism with goitre, not thyrotoxicosis. Germline TSHR activation gives hereditary non-autoimmune hyperthyroidism, not a transient postnatal course.
Reference: Nelson Textbook of Pediatrics, 22nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.