Diabetes Insipidus: A Review

Inappropriate secretion or action of serum antidiuretic hormone (ADH) is termed Diabetes Insipidus (DI), characterized by polyuria (defined as 24 hour urine output in excess of 40 ml/kg) and polydipsia [1]. As opposed to Diabetes Mellitus, where the urine is hypertonic and sweet (mellitus means honey in Greek), DI is defined as having urine that is hypotonic and bland, in the setting of polyuria. There are various mechanisms of pathogenesis of DI, all leading to the same clinical manifestation. In cases where the disorder is due to inadequate secretion of ADH, the disorder is termed Central DI, whereas when the disease is a result of renal insensitivity to ADH, the disease is termed Nephrogenic DI [1]. In cases where polyuria is due to vast amounts of ingested fluids driven primarily by behavioral or thirst disorders, it is called Primary Polydipsia (PP). Pregnant women can metabolize ADH in an accelerated manner leading to Gestational DI [2]. Overall, there are 3 cases of DI per 100,000 in the general population [3]. With regard to some familial forms of nephrogenic DI, incidence varies and some regions with common ancestry have higher incidence than other in the general population [4].