Question: If a person did not have diabetes prior to brain injury, could damage to the pituitary gland "cause" the development of diabetes? 

Answer: Diabetes insipidus can be the result of direct damage to the pituitary gland. The posterior lobe of the pituitary produces vasopression (Anti-diuretic hormone) which if not regulated or functioning properly could cause diabetes insipidus. Diabetes mellitus follows a different mechanism. Damage to the pituitary does not directly result in diabetes mellitus. The use of steroids, decreased exercise and weight gain, use of anti-seizure meds that increase insulin resistance, etc. are all secondary causes for the development of type 2 diabetes in these patients.