Patterns of amiodarone-induced thyroid dysfunction in infants and children

Heart Rhythm Society guidelines recommend obtaining thyroid function tests (TFTs) at amiodarone initiation and every 6 months thereafter in adults, with no specific pediatric recommendations. Untreated hypothyroidism in young children negatively affects brain development and somatic growth, yet the optimal screening frequency for pediatric patients remains unclear, and limited data exist on pediatric amiodarone-induced thyroid dysfunction.

The purpose of this study was to describe the patterns of amiodarone-induced thyroid dysfunction in pediatric patients.

We established a retrospective cohort of 527 pediatric patients who received amiodarone between 1997 and 2017. We defined amiodarone therapy lasting 3-30 days as "short term" and >30 days as "long term."

The final cohort (n = 150) consisted of 27 neonates (18%), 25 infants (16%), 27 young children (18%), and 71 children (47%). Of the children in whom TFTs were checked, half (50.8%) developed a thyroid-stimulating hormone (TSH) value above the reference for age. Neonates had the highest median peak TSH values in both short- and long-term groups: 23.5 mIU/L (interquartile range 11.4-63.1) and 28.8 mIU/L (interquartile range 11.4-34.4), respectively. Although concurrent use of inotropic support was significantly associated with lower initial TSH values, no variable related to cardiac illness or type of heart disease was associated with peak TSH values.

Neonates and infants receiving amiodarone had more thyroid dysfunction with greater degrees of TSH elevation than older children. TSH elevations occurred early, even with short-term exposure. Given the concern for brain development and growth in hypothyroid children, our results suggest the need for more rigorous pediatric-specific thyroid monitoring guidelines.