Outcome of Thyroid Function in Newborns from Mothers Treated with Amiodarone

Abstract

Amiodarone, a drug extensively used as an antiarrhythmic agent, contains 37% iodine and causes several thyroid abnormalities. The transplacental passage of amiodarone occurs with chronic therapy; we describe in this report the outcome of 9 pregnant women who used amiodarone (200 mg/day) for treatment of resistant tachycardia and the follow-up of their newborns. All women were clinically euthyroid at the 3rd trimester and showed expected values of thyroid hormones (mean +/- SD: total T4, 228 +/- 45 nmol/L; total T3, 4.0 +/- 0.65 nmol/L; TSH, 4.0 +/- 1.8 mU/L; negative thyroid antibodies). At birth all newborns were normal on routine examination with no goiter or corneal changes. T4 and TSH, measured on dried umbilical blood spots were normal or borderline-normal in 8 of 9 babies. Only 1 neonate presented clearly abnormal values of T4 and TSH (96 mU/L); on clinical grounds the baby was normal, without signs of hypothyroidism. At 1 month of life, T4 and TSH were normal. Follow-ups at 3, 6, and 12 months were normal. We conclude that is not necessary to discontinue treatment with amiodarone in pregnant women with resistant tachycardia, but it is imperative to evaluate the thyroid function of the newborn, since transient hypothyroidism may occur.

Developmental toxicity of thyroid-active compounds in a zebrafish embryotoxicity test

“…However, while morphological changes were observed in the present study upon exposure to amiodarone, such as the lack of an inflated swim bladder in some animals, which is included in the GDS, statistical significance could not be reached in both the GMS and GDS (data not shown). Indeed, human studies on amiodarone treated mothers indicate that transient hypothyroidism in the newborn may occur but there is no adverse effect on development (Matsumura et al, 1992;Valensise et al, 1992).…”

Amiodarone-Induced Neonatal Hypothyroidism: A Unique Form of Transient Early-Onset Hypothyroidism

“…3 There are 69 reported cases of amiodarone use during pregnancy in which the infants' thyroid function was documented. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] In all, 16 infants developed hypothyroidism 3,[5][6][7][8][9][10][11][12][13][14][15][16][17][18] ( Table 1), and two developed hyperthyroidism. 18,19 The overall incidence of hypothyroidism was 23% (16/69).…”

“…3 The effects of amiodarone during pregnancy on neonatal thyroid function have only been addressed in a limited number of reports. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] We describe two patients with transient neonatal hypothyroidism due to in utero amiodarone exposure.…”

6. Fármacos cardiovasculares na gestação e amamentação

“…A amiodarona e seus metabólitos atravessam a placenta e podem provocar complicações fetais, como hipotireoidismo e hipertireoidismo neonatal (complicações descritas em dois entre 12 neonatos de mães que usaram dose média de 325 mg/dia de amiodarona) 15 . Em outro relato do uso em 9 gestantes, com dose diária de 200 mg, foi observado um caso de hipotireoidismo transitório neonatal 24 . Outras possibilidades são bócio neonatal, peso pequeno para a idade gestacional, prematuridade, bradicardia transitória e prolongamento do intervalo QT 19 .…”