A case of diabetic ketoacidosis in a type 2 diabetic patient accompanied by Plummer's disease

A 51-year-old woman was admitted to our hospital due to nausea and upper abdominal pain. She had a consciousness disorder and tachycardia. Her laboratory data showed hyperglycemia (plasma glucose level: 694 mg/dl), ketosis (total blood ketone body level: 15.4 mmol/l) and acidemia with preserved insulin secretion and negative findings for anti-GAD antibodies. She was diagnosed with diabetic ketoacidosis, and insulin therapy was commenced. She had a nodular goiter in the left lobe of her thyroid (3×4 cm) in addition to hyperthyroidism (TSH <0.01 μ IU/l; Free T₃ 3.04 pg/ml). Thyroid autoantibodies were negative; however, ¹²³I thyroid scintigraphy revealed a hot nodule corresponding to the tumor. Plummer disease was diagnosed and hemithyroidectomy was performed. After the surgery, the patient's glycemic control was excellent and the insulin therapy was withdrawn. It is well known that the development of diabetic ketoacidosis may be accelerated by hyperthyroidism mostly caused by Basedow's disease. Clinicians should be aware of Plummer disease as a cause of hyperthyroidism during episodes of diabetic ketoacidosis in patients with type 2 diabetes mellitus.