Lower incidence of postpartum thyrotoxicosis in women with Graves disease treated by radioiodine therapy than by subtotal thyroidectomy or with antithyroid drugs.

Purpose of the Report The incidence of postpartum thyrotoxicosis (PT) in Graves disease (GD) patients treated with antithyroid drugs (ATDs) is higher than in the general population, but the incidence of PT among GD patients who had been treated with radioiodine (RI) or by subtotal thyroidectomy before their pregnancy is not well known. Subjects and Methods We reviewed the cases of women with GD who had become pregnant, and we selected the 188 women who had undergone RI therapy before the pregnancy and the 148 women who had undergone subtotal thyroidectomy for GD before the pregnancy as the subjects of this study. The ATD subjects were 107 women with GD who had become pregnant after being treated with ATDs alone before their pregnancy and were in remission before and throughout the pregnancy. Results The overall incidence of PT was 2.1% (4/188) in the RI group, 23.6% (35/148) in the subtotal thyroidectomy group, and 55.1% (59/107) in the ATD group. There were no cases of permanent thyrotoxicosis in the RI group. Conclusions The incidence of PT among women with GD who have undergone RI therapy before their pregnancy was significantly low compared to thyroidectomy group and ATD group. This finding is interesting because the incidence of PT in the RI group was lower than subtotal thyroidectomy group even though thyroid volume had been greatly reduced by thyroidectomy. RI treatment is recommended in the choice of treatment for childbearing-age women as regards the risk of postpartum recurrence.