Diabetes Insipidus

Diabetes insipidus refers to a condition of impaired regulation of water economy reflected by excessive urination with compensatory water consumption. The condition is usually caused by impaired production of vasopressin in the hypothalamus or impaired production of vasopressin receptors in the kidney. Vasopressin neurons in the supraoptic nucleus of the hypothalamus sense blood osmolarity. When osmolarity increases (e.g., after a meal, especially a salty one) vasopressin is secreted, stimulating the kidney to reabsorb more water, reducing urinary volume. Conversely, in the absence of vasopressin (usually because of damage to the hypothalamus, often associated with surgery to remove a tumor, though sometimes rarely because of a mutation in the vasopressin gene), the kidney reabsorbs relatively little water, increasing urinary volume and blood osmolarity, leading to increased thirst to compensate.