Diabetes Insipidus I: Introduction

Definition 
Diabetes insipidus is a disorder marked by the production of large amounts of dilute urine because of impaired vasopressin production, release, or kidney response. The lack of effective vasopressin action limits water reabsorption in the renal collecting ducts, which leads to excessive urinary water loss and intense thirst.

Clinical Presentation

Individuals with diabetes insipidus report persistent thirst and very high urine output. In severe cases, fluid intake can reach up to 20 liters per day. Adults often describe frequent nighttime urination, while children may present with bed-wetting. If fluid intake does not match the degree of urinary loss, rapid dehydration can develop. This may cause high serum sodium levels and neurologic changes such as irritability, confusion, seizures, or coma.

Etiology and Types

Central Diabetes Insipidus

Central diabetes insipidus happens when vasopressin synthesis or release decreases. This usually follows injury to the hypothalamus or posterior pituitary. Common causes include head trauma, neurosurgical procedures, tumors such as craniopharyngiomas, infections, autoimmune disorders, or inherited genetic variants.

Nephrogenic Diabetes Insipidus

Nephrogenic diabetes insipidus happens when the kidneys fail to respond to vasopressin. It can be present from birth because of mutations affecting vasopressin receptors or aquaporin channels. It can also appear later due to chronic kidney disease, lithium exposure, kidney infections like pyelonephritis, or electrolyte disturbances, including high calcium or low potassium levels.

Gestational Diabetes Insipidus

Gestational diabetes insipidus develops during pregnancy. The placenta produces vasopressinase, an enzyme that breaks down circulating vasopressin and lowers its effectiveness.

Primary Polydipsia

Primary polydipsia, also called dipsogenic diabetes insipidus, happens when fluid intake becomes excessively high. This pattern may relate to psychiatric conditions or hypothalamic dysfunction and suppresses vasopressin release.