Arginine Vasopressin Deficiency and Oxytocin Deficiency in the Endocrine Clinic.

The hypothalamo-neurohypophysial system consists of specialized neurons in the supraoptic and paraventricular nuclei that project to the central nervous system and the posterior pituitary, where they secrete arginine vasopressin (AVP) and oxytocin (OXT) into the systemic circulation. AVP is the key endocrine regulator of water balance via V2 receptor-mediated aquaporin-2 insertion in renal collecting ducts and modulates vascular tone via V1 receptors. OXT plays a central role in labor and lactation, but also influences metabolism, social behavior, emotional processing, and stress regulation. AVP deficiency (formerly central diabetes insipidus) results from hypothalamic-posterior pituitary disruptions or injury due to surgery, trauma, tumors, infiltrative or autoimmune disease, vascular events, or genetic causes. It is characterized by hypotonic polyuria, polydipsia, and dehydration risk, and is diagnosed by distinguishing it from AVP resistance and primary polydipsia, with copeptin-based tests providing high diagnostic accuracy. Treatment relies on desmopressin and careful education to prevent both dehydration and hyponatremia. In contrast, OXT deficiency has only recently been recognized as a potential clinical entity, particularly in patients with hypothalamic-pituitary disruptions or injury and concurrent AVP deficiency. Emerging evidence links it to social dysfunction, anxiety, and reduced quality of life. Diagnosis remains challenging due to unreliable basal OXT levels and limited stimulation tests; novel approaches, including 3,4-methylenedioxymethamphetamine (MDMA) challenge and neurophysin I as a surrogate marker, are under investigation. Preliminary studies suggest intranasal OXT may improve socioemotional outcomes, but robust evidence from randomized controlled trials is needed.