Endocrine Abstracts

Introduction: Radioiodine (RAI)-therapy for Graves’ disease (GD) is often followed by worsening autoimmunity, and the increase in TRAb may persist for several years. In pregnant women TRAb pass the placenta and may stimulate the fetal TSH receptor with a risk of fetal and neonatal hyperthyroidism.

Case report: A 21-year old woman with GD was treated with RAI, and subsequently was euthyroid with L-T4-replacement. Before RAI-therapy, TRAb was 8 U/l (reference ≤1.0 U/l). She became pregnant 4 months after RAI-therapy, and simultaneously developed opthalmopathy. Fetal tachycardia (176–180 beats/minute) developed at gestational week (GW) 33, and fetal echocardiography revealed dilated right atrium, right ventricle hypertrophy and tricuspid insufficiency with regurgitation (4–6 m/s). At GW 34+5, she delivered a severely thyreotoxic girl with FT4 >100 (12.0 – 22.0) pmol/l, FT3 > 50 (3.9–6.7) pmol/l and TSH 0.02 (0.99–7.77) mU/l. TRAb in serum of the mother and the neonate were >40 U/l. The neonate had growth acceleration without adequate weight gain (birthweight 2270 g, length 51 cm), goiter, advanced skeletal age (6 months), tachycardia (230–250 beats/minute), needed ventilatory support and developed pneumothorax. Treatment included beta-blockers, iodine, carbimazole, and later L-T4. Her condition improved, the echocardiographic findings were normalized, and she has had a normal development. Later, the mother underwent total thyroidectomy, and TRAb level declined. In a subsequent pregnancy, the fetus showed no sign of hyperthyroidism, and the neonate was euthyroid and healthy, despite elevated TRAb in cord blood (10.9 U/l).

Conclusions: This case report illustrates potential risks of RAI treatment in women with GD and documents passage of TRAb across the placenta in two successive pregnancies, with antibody-associated fetal and neonatal hyperthyroidism in the 1st pregnancy. After thyroidectomy in the mother, TRAb declined. In women who plan pregnancy, total thyroidectomy may be a better treatment option than radioiodine.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.