Diabetes Insipidus (Arginine Vasopressin Disorder)
Diabetes insipidus is the passage of excessive dilute urine because arginine vasopressin is deficient (AVP-D, formerly cranial DI) or the kidney is resistant to it (AVP-R, formerly nephrogenic DI); the immediate danger is hypernatraemic dehydration when thirst, water access or desmopressin fails.
Definition
Diabetes insipidus is a disorder of water balance with excessive production of dilute urine because AVP is deficient (arginine vasopressin deficiency, AVP-D) or the kidneys resist AVP (arginine vasopressin resistance, AVP-R). It is distinct from diabetes mellitus.
First principles
AVP and thirst conserve body water together
Arginine vasopressin (AVP, also called antidiuretic hormone) is made in the hypothalamus, stored and released from the posterior pituitary, and acts at the renal collecting duct to conserve water. Thirst provides the other half of the defence. Loss of AVP or renal resistance to it causes high-volume dilute urine; an alert person with intact thirst can often drink enough to keep the sodium near normal.
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