DIABETES INSIPIDUS - Etiology



In diabetes insipidus the urinary concentrating mechanism is impaired either as a consequence of a failure to secrete adequate amounts of vaso­pressin (central diabetes insipidus) or as a con­sequence of failure of the distal tubule and col­lecting duct to respond normally to the hormone (nephrogenic diabetes insipidus). Central diabe­tes insipidus is usually caused by head trauma, surgical hypophysectomy, granulomatous dis­eases, histiocytosis X, primary or metastatic neo­plasms, or following anoxic brain damage or men­ingoencephalitis. In at least one third of patients no pathological cause is evident. Diabetes insi­pidus following surgery or head trauma may occur transiently, may be followed by a transient period of hyponatremia due to inappropriate release of ADH from the damaged pituitary tissue, and then may resolve completely or progress to a perma­nent ADH-deficient state. Rarely central diabetes insipidus is familial, presumably due to hypopla­sia of the secretory cells in the hypothalamus. Ne­phrogenic diabetes insipidus can occur as an in­herited disorder, predominantly affecting males, or can be an acquired condition due to a variety of renal diseases, electrolyte disorders (hypoka­lemia, hypercalcemia), or drug therapies (e.g., lithium).