BACKGROUND IgG4-related disease is a systemic disease with marked infiltration of IgG4-positive plasma cells into affected organs and elevated serum IgG4. On clinical examination, swelling, nodules, and hypertrophic lesions might appear simultaneously or metachronously in different organs. CASE REPORT An 85-year-old man with sudden-onset polydipsia and polyuria insipidus was transported to our hospital because of hypothermia and general malaise. Laboratory tests revealed renal failure and central diabetes insipidus. According to his serum IgG4 level, the patient was diagnosed with possible IgG4-related kidney disease accompanied by IgG4-related hypophysitis. Abdominal contrast-enhanced computed tomography, hypophysis magnetic resonance imaging, and histological examination of the kidney were performed. Glucocorticoid therapy was administered and his renal function improved gradually. However, his central diabetes insipidus did not improve. CONCLUSIONS Glucocorticoid therapy showed different therapeutic effects on the kidney and posterior lobe of the hypophysis. It is possible that glucocorticoid therapy needs to be supported by other immunomodulatory therapies to have an effect on all affected organs.