Unlike the name suggests, diabetes insipidus is not a subtype nor in any way related to the more common sugar diabetes (diabetes mellitus). In fact, diabetes insipidus is a metabolic disorder involving the pituitary gland and the kidneys. The pituitary gland secretes ADH, anti-diuretic hormone, that allows causes aquaporins to open in the collecting duct of the nephon in the kidney. If there is no ADH, then water cannot be reabsored into the bloodstream from the kidney, so one would produce vast amounts of dilute urine. A consequence of this extraordinarily high level of urine production is the never-ending thirst of someone with this condition.
Diabetes insipidus was addressed in the TV series House MD- Season 3, Episode 16- when a young woman came in believing that she was OCD because she drank water all the time. It was deduced that she was not OCD but rather had diabetes insipidus attributed to an accident on a balance beam. How could a simple accident cause such a condition? It is possible that head trauma could damage the posterior pituitary gland where ADH is produced. If ADH production or function is inhibited or disrupted then the body will be unable to regulate its osmolarity or water concentration. This is why diabetes insipidus is characterized by excessive thirst and the production of large amounts of dilute urine. This condition can be easily misdiagnosed as portrayed in the House MD episode.