Diabetes Insipidus I: Introduction

Diabetes insipidus develops from either impaired vasopressin production or the kidneys' inability to respond to vasopressin. Central diabetes insipidus results from reduced ADH production due to brain injury or intracranial tumors. Nephrogenic diabetes insipidus occurs when kidneys cannot respond appropriately to ADH, often associated with chronic kidney disease or lithium exposure.

Diabetes insipidus presents with excessive urination, known as polyuria, and intense thirst called polydipsia. Patients excrete 10 to 20 liters of dilute urine daily compared to normal 1 to 2 liters. Adults experience marked nocturia, children may have enuresis, and rapid dehydration can develop if fluid intake does not match urinary loss.

Vasopressin, or ADH, normally promotes water reabsorption in the renal collecting ducts. Without effective vasopressin action, the kidneys cannot reabsorb water efficiently, leading to excessive urinary water loss. This results in the production of large amounts of dilute urine rather than the normal concentrated urine.

Gestational diabetes insipidus develops during pregnancy when the placenta produces vasopressinase, an enzyme that breaks down circulating vasopressin. This reduces vasopressin effectiveness and leads to polyuria and polydipsia during pregnancy. The condition typically resolves after delivery when placental enzyme production ceases.

If fluid intake does not match urinary loss, rapid dehydration develops, causing high serum sodium levels and neurologic changes. Patients may experience irritability, confusion, seizures, or coma in severe cases. Persistent fluid loss without adequate replacement poses serious health risks and requires prompt intervention.

Primary polydipsia, also called dipsogenic diabetes insipidus, occurs when fluid intake becomes excessively high. This pattern may relate to psychiatric conditions or hypothalamic dysfunction and suppresses vasopressin release. Unlike other forms of diabetes insipidus, it involves behavioral or central nervous system factors rather than hormone deficiency or kidney dysfunction.

Central diabetes insipidus results from reduced ADH production due to hypothalamic or pituitary injury. Nephrogenic diabetes insipidus occurs when kidneys fail to respond to vasopressin despite normal hormone levels. Nephrogenic causes include congenital mutations affecting vasopressin receptors, chronic kidney disease, lithium exposure, or electrolyte disturbances.