Diabetes insipidus is characterized by constitutively inadequate stimulation of ADH (antidiuretic hormone) in the kidneys. There are two variants of the disease. Central diabetes insipidus results from diminished or absent secretion of ADH by the posterior pituitary gland. Nephrogenic diabetes insipidus results from the lack of stimulation by normal levels of ADH on the V2 receptors of the renal collecting duct.