Graves Hyperthyroidism After Stopping Immunosuppressive Therapy in Type 1 Diabetic Islet Cell Recipients With Pretransplant TPO Autoantibodies

OBJECTIVE: After an initially successful islet cell transplantation, a number of patients return to C-peptide negativity, and therefore immunosuppressive therapy is discontinued. Some are then found to have developed Graves disease. We examined the risk of Graves disease after immunosuppression. RESEARCH DESIGN AND METHODS: Immunosuppressive therapy was stopped in 13 type 1 diabetic islet cell recipients who had received one course of antithymocyte globulin and maintenance doses of mycophenolate mofetil and a calcineurin inhibitor. None had a history of thyroid disease. RESULTS: In four patients, clinical Graves hyperthyroidism was observed within 21 months after discontinuation and 30–71 months after the start of immunosuppressive therapy. All four patients exhibited a pretransplant positivity for thyroid peroxidase (TPO) autoantibodies, while the nine others were TPO negative pre- and posttransplantation. CONCLUSIONS: Type 1 diabetic recipients of islet cell grafts with pretransplant TPO autoantibody positivity exhibit a high risk for developing Graves hyperthyroidism after immunosuppressive therapy is discontinued for a failing graft.