Introduction: Neonatal hyperthyroidism is a rare condition with significant sequela and up to 25% mortality if left untreated. Maternal hyperthyroidism occurs in 0.2-1.0% of pregnancies, most commonly due to Graves’ disease. Neonatal thyrotoxicosis, due to transplacental transfer of thyroid stimulating hormone (TSH) receptor antibodies (TRAbs), is seen in 1-5% of neonates born to mothers with Graves’ disease.
Case summary: Ms K.F. is a 33 year old lady referred to endocrine in pregnancy clinic for management of hypothyroidism. Ms K.F’s first trimester TSH was elevated at 3.15 pmol/L. On detailed questioning Ms K.F. revealed a significant history of Graves’ disease with ophthalmopathy for which she had a thyroidectomy and ocular surgery. On further testing the TRAb titre was found to be markedly elevated at 37.7 IU/L. Ms K.F. and her foetus were closely monitored throughout the pregnancy noting borderline foetal tachycardia. Severe neonatal thyrotoxicosis ensued, requiring a 2 week admission. This diagnosis was delayed due to inadequate neonatal testing. I will elaborate on the case including a review of the literature and discuss potential pitfalls in diagnosis of maternal Graves’ disease and neonatal thyrotoxicosis.