GRAVES-DISEASE FOLLOWING THYROTOXIC PAINLESS THYROIDITIS - ANALYSIS OF ANTIBODY ACTIVITIES AGAINST THE THYROTROPIN RECEPTOR IN 2 CASES

The exact immunologic mechanisms that lead to the emergence and progre ssion of painless (''silent'') thyroiditis remain unclear. We report t wo cases of painless postpartum thyroiditis followed by Graves' diseas e, where extensive immunologic evaluation supported a possible pathoge netic association. The time course of changes in thyroid function test s, I-123 thyroidal uptake values, and thyrotropin receptor antibodies (TSHRAbs) were documented. The existence of stimulating TSHRAbs (TSAbs ) activating the cyclic adenosine monophosphate (cAMP) and phosphatidy linositol 4,5-bisphosphate (PIP2) signal cascades and their functional epitopes, as well as two different thyrotropin-binding inhibitory imm unoglobulins (TBII) were documented in both patients at the time of di agnosis of Graves' disease. We suggest that susceptible persons may de velop an immunologic response that can trigger the appearance of a mix ture of species of TSHRAbs, which in turn may lead to the sequential o ccurrence of painless thyroiditis and Graves' disease. Additionally, t he multiple phases of hyperthyroidism and hypothyroidism that can occu r in these patients may reflect the existence and changing spectrum of TSHRAbs in their sera.