A 45-year-old man presented with anterior pituitary failure, requiring thyroxine, hydrocortisone and androgen replacement. An MRI scan revealed a large cystic pituitary mass and thickening of the pituitary stalk. Over three years, diabetes insipidus and bitemporal hemianopia developed and the cystic mass had enlarged on MR scanning. Transphenoidal resection was performed with normalisation of the visual fields. Histology revealed lymphocytic hypophysitis, which is rare in men. The presentation with cystic enlargement is unique.