A disease of the pituitary gland or kidney, not diabetes mellitus. Diabetes insipidus is often called "water diabetes" to set it apart from "sugar diabetes." The cause and treatment are not the same as for diabetes mellitus. "Water diabetes" has diabetes in its name because most people who have it show most of the same signs as someone with diabetes mellitus-they have to urinate often, get very thirsty and hungry, and feel weak. However, they do not have glucose (sugar) in their urine.