Hypopituitarism Possibly due to Lymphocytic Hypophysitis in a Patient with Type 1 Diabetes

Hypopituitarism often develops insidiously, and undiagnosed hypopituitarism can influence the glycemic profile of patients with type 1 diabetes. We herein report the case of a 49-year-old man with type 1 diabetes and Hashimoto's thyroiditis who experienced an unexplained improvement in his glycemic level and recurrent severe hypoglycemia, despite a reduction in the dose of insulin. Based on the patient's endocrinological findings, he was diagnosed with hypopituitarism possibly due to lymphocytic hypophysitis, as supported by positive results for human leukocyte antigen A24 and Cw3. Following the administration of hydrocortisone replacement therapy, his insulin requirement increased to a premorbid level, and the severe hypoglycemia resolved.