Radioiodine Therapy of Graves' Disease in Women with Childbearing Potential and the Pre-Conceptional Counseling About Antithyroid Drugs.

Graves' disease and hyperthyroidism in women with childbearing potential are a challenge in pre-conceptional counseling. The non-surgical alternatives are radioiodine therapy or antithyroid drugs. Here, we focus on the TSH receptor antibody (TRAb) level-without or after radioiodine therapy-and the probability of fetal or neonatal hyperthyroidism. This immunological effect should be weighed against the risk of congenital malformation taking propylthiouracil during pregnancy. For up to 2 years after radioiodine therapy for Graves' disease, TRAb levels may remain above the pre-therapeutic level. The time of conception after radioiodine therapy and a high TRAb level are associated with the likelihood of neonatal hyperthyroidism: 8.8% probability if conception occurred 6-12 months after radioiodine therapy, with a 5.5% probability for 12-18 months, and 3.6% probability for 18-24 months. The TRAb value above 10 U/L in the third trimester is the main risk factor for neonatal hyperthyroidism. If a woman does not wish to postpone her family planning, the pre-conceptional counseling has to describe the risk of propylthiouracil, thiamazole, or of an uncontrolled hyperthyroidism. According to some national cohort studies (Danish, Swedish, Korean), the risk for fetal malformations (ear, urinary tract) under propylthiouracil is increased by 1.1-1.6%, in addition to the spontaneous risk for unexposed pregnant women. For thiamazole, the additional risk for fetal malformation was about 2-3%, depending on the dose of thiamazole. Propylthiouracil has posed a lower risk for congenital malformation than an uncontrolled hyperthyroidism. To minimize the risk for the newborn, women with Graves' disease and hyperthyroidism should offer a definitive therapy strategy (e.g., radioiodine therapy) long before planning a pregnancy.