Diagnosis and treatment of thyrotoxicosis during pregnancy and lactation

Poorly treated or untreated maternal overt hyperthyroidism may affect pregnancy outcome. Thyroid dysfunction and hyperthyroidism is present in about 0.3% and 2-3% of pregnancies respectively. Thyroid hyperfunction and hypofunction are more prevalent and usually go unrecognized. If thyroid dysfunction remained undiagnosed and has not been treated appropriately, would result in serious adverse pregnancy outcomes and treat both mother and her fetus. The aim of this review is to mention many aspects of hyperthyroidism in pregnancy and lactation in depth. Literature review was performed using MEDLINE between years 1960 and 2010, with the terms “Hyperthyroidism and pregnancy”, “Anti-thyroid drug and pregnancy”, “Radioiodine and pregnancy”, “Hyperthyroidism and lactation”, “Anti-thyroid drug and lactation”, both separately and in conjunction with the terms “fetus”, “neonate” and “maternal”. We selected Proper study design of survey, case control and cohort studies, and clinical trials and review papers if the authors had at least four articles of their own in the list of references of review paper. The strategy used to search for articles was developed with the assistance of a research librarian. Antithyroid drugs are the main therapy of maternal hyperthyroidism during the lactation. All forms of antithyroid drugs can be used in pregnancy. As there are some reports regarding teratogenicity of methimazole (MMI), Propylthiouracil (PTU) is preferred in the first trimester and should be replaced by MMI after this trimester. Radioiodine is absolutely contraindicated for treatment of hyperthyroidism in pregnancy. Subtotal thyroidectomy in second trimester is indicated if hyperthyroidism is uncontrolled. MMI is the mainstay of the treatment of postpartum hyperthyroidism, in particular during lactation. ‍ Management of hyperthyroidism during pregnancy requires special considerations because maternal thyroid disease could have adverse effects on the mother, fetus and neonate.