When there is a change in blood volume, ionic concentration, or excessive fluid loss, osmoreceptors are activated, causing the neurohypophysis to release vasopressin or antidiuretic hormone (ADH). ADH stimulates water reabsorption from the distal parts of the tubules, preventing water loss and diuresis. Osmoreceptors are turned off when enough body fluid and ADH release is suppressed. ADH can also cause blood vessel constriction, raising blood pressure and increasing blood flow in the glomerulus and glomerular filtration rates.