IMPE Abstracts

Introduction: Neonatal hyperthyroidism is a rare condition frequently caused by the transplacental passage of TSH receptor antibodies (TRAb) from mothers affected by Graves’ disease (GD). Hyperthyroidism may occur in 1 to 8% of children born to women with this condition. The effects of maternal hyperthyroidism in the foetal developing brain are known to have deleterious effects. After birth, neuropsychological manifestations of overt hyperthyroidism are reverted with the normalisation of thyroid function using antithyroid drugs, however, whether hyperthyroidism treated early in life has any long-term consequences is currently not known.

Objective: The aim of this study is to evaluate the impact of neonatal hyperthyroidism on cognitive, behavioural and social development in children born to mothers with GD, and to investigate whether they have impaired social communication, executive functioning and/or behaviour.

Methods: Cases were identified by diagnosis through the electronic medical records and controls were recruited from the patient’s siblings or friends. Primary caregivers completed a demographic and background information questionnaire, and parent report measures of executive functioning (Behaviour Rating Inventory of Executive Function) and behaviour (Strengths and Difficulties Questionnaire).

Results: Twenty-one hyperthyroid neonates born to 15 mothers were identified, 12 (57%) female. Gestational age was 37 ±1.8 weeks and birth weight 2.74 ±0.3 kg. All received antithyroid drugs from 5.4 ±4.5 days of life during 47.2 ±27.9 days. Five cases met the inclusion criteria and agreed to participate, and were compared to 5 controls matched by age and gender, at the age of 6.6 ±1.3 and 6.4 ±1.7, respectively. Cases performed worse in the Behavior Regulation Index (BRI) (60,6 ±10,7 vs 43,8 ±5,6; P=0.007) (ability to regulate and monitor behaviour effectively) and Cognitive Regulation Index (CRI) (60,6 ±13,0 vs 47,2 ±5,9; P=0.034) (control and manage cognitive processes and problem solve effectively). Additionally, cases scored higher on the SDQ hyperactivity scale (4,4 ±1,5 vs 2,0 ±1,4; P=0.016) and on the externalising scale which sums the conduct and hyperactivity scales, as in the total difficulties score (7,6 ±4,6 vs 3,0 ±1,9; P= 0.036).

Conclusion: In this small cohort, children with neonatal hyperthyroidism treated with antithyroid drugs were rated by parents as having poorer executive functioning skills and more behavioural problems. Possible explanations might be early exposure to hyperthyroidism in utero and/or brief hypothyroidism induced by overtreatment with antithyroid drugs during infancy. Further research with larger sample sizes may clarify possible hypotheses.