DIABETES INSIPIDUS - A disorder where there is increased urination (3-15 liters per day) accompanied by uncontrollable thirst which occurs secondary to the inadequate secretion of antidiuretic hormone (vasopressin) by the posterior pituitary gland. Diabetes insipidus is seen more common in the younger patient. There are two forms of diabetes insipidus (DI): central and nephrogenic. In central DI there is not enough ADH secreted by the posterior pituitary gland. In the nephrogenic form, ADH that is secreted (often in increased quantities) by the posterior pituitary gland fails to exert its normal effect on the receptors located within the kidney. This is due to a defect in the distal tubule of the kidney.