Central diabetes insipidus (CDI) is a rare disorder characterized by excessive thirst (polydipsia) and excessive urination (polyuria). It is not related to the more common diabetes mellitus (sugar diabetes), in which the body does not produce or properly use insulin. CDI is a distinct disorder caused by complete or partial deficiency of the protein, arginine vasopressin (AVP), which is required by the kidneys to manage water balance in the body. If affected individuals do not have access to water, dehydration may occur. Eventually, more serious symptoms can develop including changes in consciousness and confusion associated with dehydration and elevation in serum sodium concentration (hypertonic dehydration). CDI may be caused by any condition that affects the creation, transport or release of vasopressin. CDI may be inherited or acquired. In some cases, no cause can be identified (idiopathic).