Thyroid physiology and autoimmunity in pregnancy and after delivery

During pregnancy and after delivery, the maternal thyroid gland faces several metabolic, hemodynamic and immunologic changes. In this article we first summarize the current knowledge on the physiologic adaptation of the healthy thyroid to pregnancy, including variations of thyroid-stimulating hormone and free thyroid hormones, as well as variations of thyroid volume. Our second aim is to illustrate the background of thyroid autoimmunity in this period, which characteristically ameliorates during pregnancy and aggravates after delivery. Although rare during pregnancy, Graves' disease is the most frequent cause of hyperthyroidism, while Hashimoto's thyroiditis is the most frequent cause for hypothyroidism. Both types of thyroid dysfunction may lead to detrimental complications in mother and child and therefore timely recognition and treatment is essential. Postpartum autoimmunity most frequently exacerbates in the form of postpartum thyroiditis, which presents with diverse clinical presentations and may lead to permanent hypothyroidism.