Hypothyroidism and Hyperthyroidism

Hypothyroidism complicates 1-3 in 1000 pregnancies. Women with overt hypothyroidism are at an increased risk for complications such as early pregnancy failure, preeclampsia, placental abruption, low birthweight, and stillbirth. Treatment of women with hypothyroidism has been associated with improved pregnancy outcomes. The most common cause of primary hypothyroidism in pregnancy is chronic autoimmune thyroiditis (Hashimoto thyroiditis). This is a painless inflammation with progressive enlargement of the thyroid gland which is characterized by diffuse lymphocytic infiltration, fibrosis, parenchymal atrophy, and eosinophilic change. Other important causes of primary hypothyroidism include endemic iodine deficiency and a history of either ablative radio-iodine therapy or thyroidectomy. Hyperthyroidism complicates approximately 1-2 in 1000 pregnancies. The overwhelming cause of hyperthyroidism during pregnancy is Graves disease or autoimmune thyrotoxicosis. Pregnant women with hyperthyroidism are at increased risk for congestive heart failure, thyroid storm, preterm labor, preeclampsia, fetal growth restriction, and perinatal mortality. Treatment of hyperthyroid women to achieve adequate metabolic control will result in improved pregnancy outcomes.