A 73-year-old woman was admitted due to weight loss and generalized malaise. The basal levels of all the anterior pituitary hormones, except for prolactin, were reduced. However, they were all elevated in response to exogenous hypothalamic hormones. After starting hydrocortisone replacement, the patient had polyuria of >5,000 mL/day. T1-weighted MRI depicted a low signal of an oval mass in the sella turcica and an iso-intense signal of another mass at the pituitary stalk. These findings indicate a hypothalamic type of hypopituitarism and masked central diabetes insipidus which possibly derived from the atypical occupation of Rathke's cleft cyst at the pituitary stalk.