Hypothalamic obesity due to hydrocephalus caused by aqueductal stenosis. A case is presented of 14 year old female with hypothalamic obesity due to hydrocephalus caused by aqueductal stenosis. Evidence of hypothalamic obesity included 1) acute hyperphagia and weight gain, 2) neuroradiology showed hydrocephalus with focal enlargement of the third ventricle, 3) endocrinological studies revealed hyperinsulinaemia and impaired growth hormone (GH) response to arginine, but normal GH response to growth hormone-releasing factor (GRF) and 4) Torkildsen's ventriculo-cisternal shunting resulted in improvement in hyperphagia and obesity. 