Although the factors that cause developments or exacerbations of autoimmune thyroid dysfunction are not known, the changes of glucocorticoids might modulate the autoimmune responses. We compared the postoperative changes in thyroid function in one patient with Carney's complex with primary adrenocortical nodular dysplasia (PAND) and 19 patients with Cushing's disease due to ACTH-producing pituitary adenoma. Thyroid dysfunction developed after surgery for glucocorticoid excess in two patients; one with Carney's complex had transient hypothyroidism after bilateral adrenalectomy for PAND, and the other had transient hyperthyroidism due to thyroiditis after removal of ACTH-producing pituitary adenoma for Cushing's disease. Both patients had no thyroid autoantibodies at the time of surgery. None of the remaining 18 patients had clinically evident thyroid disease or increased antithyroidantibody titers. Development of autoimmune thyroid dysfunction may be observed after surgery for glucocorticoid excess in the patients with any forms of Cushing's syndrome, even who do not have thyroid antibodies.