(CSEMP003) CASE REPORT: UNCONTROLLED HYPERTHYROIDISM IN PREGNANCY ASSOCIATED WITH FETAL HEART MALFORMATION

Background: Hyperthyroidism is an uncommon condition that complicates approximately 0.1% to 0.4% of pregnancies. It carries with it high morbidity and mortality for mother and fetus due to several factors, including transplacental passage of maternal thyroid stimulating antibodies or thyrostatic agents. Both of these may disrupt fetal thyroid function. Hyperthyroid heart disease can harm both the mother and the foetus, resulting in severe heart failure.

METHODS AND RESULTS: Clinical Presentation: A 24-year-old pregnant woman at 29+6 weeks gestation presented to the Emergency Room (ER) with left abdominal pain. Fetal ultrasound revealed fetal tachycardia (heart rate (HR) > 200bpm). She had a previous pregnancy in 2021 without any complications. She was known to have a goiter since childhood, but had never been diagnosed with thyroid dysfunction. Family history was unremarkable.
On initial assessment, she was found to have tachycardia (HR 120bpm), resting tremor and a goiter associated with mild compression symptoms and mild proptosis. She also noted having no weight gain during her pregnancy. Initial investigations confirmed overt hyperthyroidism with a suppressed thyroid stimulation hormone (TSH) level of < 0.02 mlU/L and a high free thyroxine (T4) of 51.9 pmol/L (8-18). A fetal ultrasound was done, demonstrating persistent fetal tachycardia with goiter. Echocardiogram showed a dilated right atrium (RA), wide but compressed right ventricle (RV) and left ventricle (LV), aortic arch hypoplasia, tricuspid regurgitation, and bilateral pleural effusion.
The patient was started on Propylthiouracil (PTU) and Metoprolol and doses were titrated based on fT4. Once the thyrotoxicosis was controlled, the fetal ultrasound (US) showed improved pleural effusions. The patient delivered at 30 weeks gestation and was discharged home with a highly suspected diagnosis of Graves’ disease. The baby is still in the intensive care unit (ICU) and is being treated with methimazole due to fetal hyperthyroidism.

Conclusion: Identification and adequate management of hyperthyroidism in pregnant women is essential, as uncontrolled thyrotoxicosis significantly increases the risk of maternal and fetal complications. Although rare, offspring of mothers with Graves’ disease may develop fetal/neonatal hyperthyroidism. The management of hyperthyroidism in pregnancy requires a close collaboration between endocrinologists, obstetricians, and neonatologists.