Synopsis
Diagnose and manage central arginine vasopressin deficiency while preventing life-threatening dehydration, hypernatraemia and desmopressin-associated water intoxication.
- Confirm true polyuria by measured urine volume before assuming thirst or urinary frequency represents central diabetes insipidus.
- Exclude osmotic diuresis, excess drinking, kidney disease, hypercalcaemia, hypokalaemia and medicines before testing the vasopressin axis.
- In decompensated AVP deficiency, restore fluid first; if excessive dilute urine persists, Society for Endocrinology guidance advises desmopressin 1–2 micrograms IV or IM, with close clinical, urine-output and serum-sodium monitoring.
- A person with intact thirst and unrestricted water may maintain normal sodium despite severe AVP deficiency, so normal sodium does not exclude the diagnosis.
- Water-deprivation, copeptin-based and desmopressin-response testing belong in a specialist supervised protocol because dehydration and sodium shifts can harm.
- Desmopressin is life-sustaining for complete central disease, but missed doses cause water loss and excess doses or drinking without thirst cause water retention.
- After pituitary surgery, distinguish transient AVP deficiency from the possible triphasic response and monitor sodium rather than prescribing an automatic fixed course.
- Every hospital admission should identify
Investigation priorities
Confirm genuine polyuria and quantify severity before endocrine provocation.
Management branches
Persistent thirst and high urine output occur without acute dehydration.
- Measure urine volume and review glucose, electrolytes, renal function, diuretics, lithium and deliberate high fluid intake.
- Obtain paired plasma sodium or osmolality and urine osmolality under documented conditions, avoiding self-imposed dehydration.
- Refer for validated specialist dynamic testing and pituitary assessment when hypotonic polyuria remains unexplained, then image according to the biochemical and clinical question.
Key medicines
DesmopressinContinue the person's verified stable formulation and dose when safe; Society guidance lists typical oral or sublingual doses of 100–200 micrograms and intranasal doses of 10–20 micrograms. In decompensated AVP deficiency, restore fluid first, then give 1–2 micrograms IV or IM if excessive dilute urine persists and reassess before repeating.Oral, melt, nasal and injectable doses are not equivalent. Excess treatment with fluid intake causes hyponatraemia; omission causes hypernatraemic dehydration. Nasal absorption varies with rhinitis, and intravenous dosing requires close sodium and urine monitoring.