Silent thyroiditis in uncommon setting.

The most common causes of thyrotoxicosis in Japan are silent thyroiditis and Graves’ disease. For patients with thyrotoxicosis present in early pregnancy, both gestational thyrotoxicosis and undiagnosed Graves’ disease must be considered. Silent thyroiditis is a rare condition during pregnancy. Postpartum thyroiditis is a variant of silent thyroiditis that occurs in the postpartum period, a few months after delivery, and occasionally as long as 1 year later. The development of postpartum thyroid disease might be due to suppression of the immune system during pregnancy, with a subsequent rebound of immune-competence after delivery. It is not uncommon to find women who have started on their next pregnancy within this transient thyrotoxicosis. In this issue of Internal Medicine (1) Sato et al discuss thyrotoxicosis in the first trimester of pregnancy with this time frame. Overt thyrotoxicosis has an impact on pregnancy outcomes and offspring development. Silent thyroiditis, however uncommon in pregnancy, must be differentiated from Graves’ disease.