Introduction: Amiodarone (AMD) is an antiarrhythmic agent which contains 37% of iodine. It can reach the fetus by transplacental passage and induce transient congenital hypothyroidism (TCH). We report two cases of TCH caused by gestational exposure to AMD, detected by the Newborn Screening Program for Congenital Hypothyroidism of the State of Paraná-Brazil. CLINICAL CASE 1 (C1): Neonatal TSH value was 78.2 mU/L (normal<15 mU/L). AMD had been given to the mother during pregnancy to treat maternal arrhythmia. The screening results were confirmed by serum thyroid function tests. Levothyroxin (L-T4) (50 microg/day) was started on the first visit, on the 14th day of life (dl). CLINICAL CASE 2 (C2): Neonatal TSH value was 134.0 mU/L. AMD had been given to the mother in the third trimester of pregnancy to treat maternal arrhythmia. The screening results were confirmed by serum thyroid function tests: L-T4 (50 microg/day) was started on the first visit, with 13 dl.
Follow-up: TSH and T4 normalized on 51 dl (C1) and 36 dl (C2); L-T4 could be diminished gradually and stopped within 16 months (C1) and 10 months (C2). They were followed-up until 22 months (C1) and 16 months (C2) with normal thyroid function tests. Their growth and mental development, evaluated by the Cognitive Adaptive Test/Clinical Linguistic & Auditory Milestone Scale (CAT/CLAMS test), were normal.
Conclusion: Evaluation of thyroid function and mental development should be performed if AMD is used during pregnancy. Treatment of TCH must be started as soon as the diagnosis is made.