Endocrine Abstracts

Context: Postpartum hyperthyroidism (PH) is one of the postpartum thyroid disorders that occurs during the first year postpartum and PH is caused by destructive thyroiditis and recurrent Graves’ disease. PH is an exacerbation of an underlying autoimmune thyroiditis that is aggravated by the immunological rebound that follows the partial immunosuppression that occurs during pregnancy. The prevalence of PH among women with Graves’ disease (GD) who had been treated with radioiodine (RI) before their pregnancy has never been investigated.

Objective: Our objective was to determine the prevalence of PH among women who had been diagnosed with GD and undergone RI therapy before their pregnancy.

Subjects and methods: We reviewed the cases of women with GD who became pregnant between January 1, 1999 and December 31, 2010, and selected the 188 women who had undergone RI therapy before the pregnancy as the subjects of this study. Of the 188 women, 110 were on replacement therapy with levothyroxine (25–175 μg/day, mean 87.5 μg/day) (Group 1) and 78 were euthyroid without medication (Group 2). The control subjects were 107 women who became pregnant during 2009 who had been treated with antithyroid drugs and were in remission throughout the pregnancy. All subjects were followed up for at least one year after delivery. We monitored the TSH receptor antibody (TBII) level of all of the women during pregnancy and the postpartum period.

Result: Transient hyperthyroidism was observed in one of the 110 women in Group 1 (0.9%) and in three of the 78 women in Group 2 (3.8%). No cases of permanent hyperthyroidism were observed in either Group 1 or Group 2. PH was observed in 59 of the 107 women (55%) in the control group. In 41 of the 57 women it was transient hyperthyroidism, and in the other 18 it was recurrent Graves’ disease and required medication. After delivery the TBII level increased in 15 cases in Group 1, in 19 cases in Group 2, and in 34 cases in the control group.

Conclusion: The results of this study provided evidence that RI treatment before pregnancy is effective in preventing PH.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector