Vasopressin is a hormone produced by the pituitary gland. It assists with the regulation of the volume of water, glucose and salts in the body. Its primary action is suppressing kidney function and the production of urine, resulting in the body retaining water, salt and glucose. It also constricts blood vessels.
Vasopressin is released by the pituitary when the overall volume of the blood vessels starts to drop.
A lack of vasopressin in the body leads to diabetes insipidus, characterized by frequent urination and constant thirst, but without the high urine glucose levels of diabetes mellitus. Too much vasopressin will lead to extremely low sodium levels. The most common cause of excess vasopressin is SIADH, a Paraneoplastic syndrome.
Vasopressin conditions can be treated with synthetic vasopression for low levels, and vasopressin antagonists for high levels.