Lithium‐induced Hashimoto’s encephalopathy: a case report

Objective: To report on a patient with Hashimoto’s encephalopathy induced by lithium. Patient and interventions: A 61‐year‐old woman with a type II bipolar disorder and a history of lithium‐induced thyrotoxicosis associated with silent thyroiditis was hospitalized to treat a severe major depressive episode. Given long‐term treatment with levothyroxine for hypothyroidism that had resulted from silent thyroiditis, endogenous hormone in thyroid follicles was assumed to be minimized by the negative feedback, decreasing risk of recurrent thyrotoxicosis if lithium were restarted. Results: Lithium clearly relieved the patient’s depressive symptoms, but after 40 days encephalopathy developed. Thyrotoxicosis was ruled out, and serum antithyroid antibody titers were elevated. In the cerebrospinal fluid, protein content was substantially elevated and antithyroid antibodies were detected. Encephalopathy resolved dramatically after course of intravenous pulse therapy with methylprednisolone. Conclusions: We believe that autoantibodies against antigens shared by the thyroid gland and the brain were induced by exposure to lithium, causing the patient to develop Hashimoto’s encephalopathy.