Thyroid Diseases During Pregnancy

Abstract

Pregnancy is associated with various changes in thyroid metabolism: increase in thyroxin-binding globulin, decrease in thyroid-stimulating hormone (TSH), and increase in total thyroxin concentration as well as in iodine requirements. Here, we provide an overview of pregnancy-associated thyroid diseases with a focus on the risks for mother and child as well as current recommendations for diagnosis and treatment. There are new upper TSH values recommended for the definition and treatment indication of hypothyroidism during pregnancy, while the presence of anti-TPO antibodies plays a role in decision-making. Since hypothyroidism has been associated with adverse outcomes for both the mother and offspring, substitution is needed not only for manifest hypothyroidism but also for latent hypothyroidism in special situations. In the presence of anti-TPO antibodies with normal thyroid status, regular monitoring for TSH is required. A relevant cause of hyperthyroidism during pregnancy is Graves’ disease, which has to be differentiated from gestational hyperthyroidism. Antithyroid drugs are recommended in the lowest effective dose for Graves’ disease with overt hyperthyroidism, so that fT4 is kept in the upper normal range and TSH remains suppressed. The indication and risks of various antithyroid drugs are discussed here. In special situations, TRAK controls and sonographic monitoring of the fetus are mandatory. Postpartum thyroiditis (PPT) has a biphasic course, with a transient thyrotoxic phase in the first 6 months, followed by hypothyroidism and possible return to the euthyroid state 1 year postpartum. If a differentiated thyroid cancer is diagnosed during pregnancy, surgery can usually be safely postponed until after delivery. Furthermore, the importance of iodine deficiency and the recommendations for an optimal iodine intake during pregnancy, as well as current indications for thyroid screening, are highlighted.