ESPE Abstracts

Objective: Neonatal hyperthyroidism is a severe but generally transient condition with a 2% prevalence in offspring of mothers affected by Graves' disease. It is caused by the transplacental passage of maternal anti-thyrotropin receptor stimulant antibodies (TRABs). Here we report the cases diagnosed at our centre between 2015-2019 in order to re-evaluate the diagnostic and therapeutic approach to this challenging neonatal thyroid alteration.

Methods: The study was conducted on a cohort of twenty newborns diagnosed with neonatal hyperthyroidism. All had mothers who were or had been affected by Graves disease. We collected the records of the maternal disease and treatment during pregnancy along with data regarding the birth, diagnosis, and treatment of the newborn.

Results: Three mothers (15%) underwent total thyroidectomy and were in substitutive treatment with L-Thyroxine during pregnancy. None of these three cases had available maternal TRABs values. In 3rd-4th days of life these three newborns developed hormonal and clinical signs (hypertonus/exophthalmus/tachycardia) of hyperthyroidism with an important elevation of TRAB values (>17 to 72 times the upper reference limit). Thus Methimazole (MMZ) was started and associated, in two cases, with a beta-blocker therapy.

An anti-thyroid drug (MMZ or Propiltiouracile) was prescribed before or during the gestation in seventeen mothers (85%). Maternal TRAB values were only reported in eight pregnancies, all resulting positive. Between the 3rd and 21st day of life the diagnosis of neonatal hyperthyroidism was confirmed by thyroid function tests; neonatal TRABs values resulted positive in all the newborns. MMZ treatment was started in nine infants (53%) while the others had a spontaneous remission.

Conclusions: The determination of maternal TRABs levels is essential in order to identify the newborns at risk of developing neonatal hyperthyroidism, a rare and potentially life-threatening condition. Nevertheless, this dosage is often disregarded, especially in mothers that previously underwent a total thyroidectomy. We observed that elevated neonatal TRABs values seem to be associated with more severe clinical and hormonal features requiring treatment. Less severe and belated forms are generally present in the offspring of mothers taking anti-thyroid drugs, with lower neonatal TRABs levels and not always requiring anti-thyroid therapy.