Diabetes insipidus (arginine vasopressin deficiency and resistance)

Arginine vasopressin (AVP) is a critical hormone in the regulation of water balance and vascular tone. Synthesized in the hypothalamus and released from the posterior pituitary, AVP acts primarily on V2 receptors in the renal collecting ducts to promote water reabsorption via aquaporin-2 (AQP-2) channels, and on V1 receptors to mediate vasoconstriction. Disorders of AVP production or action manifest clinically as diabetes insipidus (DI), more recently termed AVP deficiency (AVP-D) and AVP resistance (AVP-R). These conditions are characterized by hypotonic polyuria and compensatory polydipsia.

Current diagnostic approaches include the water deprivation test (WDT) and hypertonic saline infusion with copeptin assessment, with increasing emphasis on the utility of copeptin as a stable and reliable biomarker for distinguishing between AVP deficiency (AVP-D), AVP resistance (AVP-R), and primary polydipsia (PP). Management of AVP-D relies on desmopressin (dDAVP), with careful titration to avoid hyponatraemia. AVP-R requires fluid management and pharmacologic interventions including thiazide diuretics and non-steroidal anti-inflammatory drugs. Additional subtypes of DI, such as gestational DI and adipsic hypernatraemia, present specific diagnostic and treatment complexities.