Postpartum thyroiditis is a type of thyroiditis, inflammation of the thyroid, occuring in the first 12 months after pregnancy and typically involves hyperthyroidism followed by hypothyroidism which is most often temporary.
Postpartum thyroiditis is believed to result from the modifications to the immune system necessary in pregnancy, and histologically is the same as subacute lymphocytic thyroiditis also called silent thyroiditis or painless thyroiditis, a form of subacute thyroiditis. The process is normally self-limiting, but when thyroid antibodies are found there is a high chance of this proceeding to permanent hypothyroidism.