Autoimmune hyperthyroidism due to secondary adrenal insufficiency: resolution with glucocorticoids.

OBJECTIVE: To describe the course of autoimmune hyperthyroid disease in a patient with corticotropin (ACTH) deficiency treated with glucocorticoids. METHODS: We report the clinical presentation, laboratory data, imaging studies, and management of a patient with weight loss, fatigue, apathy, hallucinations, and arthritis. RESULTS: Autoimmune hyperthyroidism (positive thyroperoxidase and thyroglobulin antibodies and borderline positive thyrotropin receptor antibody) was diagnosed in a 71-year-old woman. New psychotic symptoms prompted brain magnetic resonance imaging, which revealed a partially empty sella. Undetectable morning cortisol, undetectable ACTH, and failure to stimulate cortisol with synthetic ACTH (cosyntropin 250 mcg) secured the diagnosis of long-standing secondary adrenal insufficiency. Hydrocortisone replacement improved the patient's symptoms, resolved the thyroid disease, and decreased thyroid antibody titers. In retrospect, the patient recalled severe postpartum hemorrhage requiring blood transfusion at age 38 years. A Sheehan event probably occurred 33 years before the patient presented with corticotropin deficiency. Hyperthyroidism accelerated cortisol metabolism and provoked symptoms of adrenal insufficiency. CONCLUSIONS: The hypocortisolemic state may precipitate hyperimmunity and autoimmune thyroid disease. Rapid resolution of hyperthyroidism and decreased thyroid antibody titers with glucocorticoid treatment support this hypothesis.