The clinical expression of postpartum thyroid autoimmune disease in women with a history of Graves' disease, varies and includes Graves' hyperthyroidism, silent thyroiditis, and silent thyroiditis followed by Graves' hyperthyroidism. Momotani, Tokyo, Japan, studied two pregnancies in 12 women with a history of Graves' disease. It was found that a same woman manifested the same forms of postpartum thyroid disease: 5 women only Graves' disease, 6 women only silent thyroiditis, and 1woman Graves' disease following silent thyroiditis. There was no relationship between the form of thyroid disease and the thyrotropin binding inhibiting immunoglobulins (TBII) result around the time of conception or near term. It is concluded that genetic factors rather than the activity of Graves' disease before or during pregnancy determine the type of postpartum thyroid disease. Janssen et al., Ann Arbor, MI, and Washington, DC, USA, evaluated TPO antibodies and Tg antibodies in 53 patients with postpartum thyroiditis (PPT) at the time of diagnosis and during follow-up over 5years. 49/53 patients had TPO antibodies in a titer 1:400 or greater, and only 7/53 had antibodies to TG. Patients, who became hypothyroid, had high TPO antibodies. The frequency of two TPO antibodies with different epitopes was similar as in Hashimoto's disease, indicative of a similar immune response to TPO in PPT and Hashimoto's disease. Amino, Osaka, Japan, found that the presence of thyroid stimulating antibodies (TSAb) in patients, positive for TPO antibodies, was highly predictive for the development of postpartum Graves' disease. Thus, 5 out of 7 of those patients developed Graves' disease, whereas 64 TSAb negative TPO positive patients did not develop postpartum Graves' disease, but 44/64 developed other forms of postpartum autoimmune thyroiditis. It is concluded that, when TSAb is positive in patients, having TPO antibodies, they are at high risk for the development of postpartum Graves' hyperthyroidism.