neurohypophysis /-hīpof″isis/ [Gk, neuron + hypo, under, phyein, to grow] , the posterior lobe of the pituitary gland that is the release point of antidiuretic hormone (ADH) and oxytocin. Nervous stimulation from the hypothalamus controls the release of the substances into the blood. When stimulated by the hypothalamus, the neurohypophysis releases ADH by an increase in the osmotic pressure of extracellular fluid in the body. The hormone acts on the cells in the distal and collecting tubules of the kidneys, making them more permeable to water and thus reducing the volume of urine. The neurohypophysis releases oxytocin under appropriate stimulation from the hypothalamus. Oxytocin produces powerful contractions of the pregnant uterus and causes milk to flow from lactating breasts. Stimulation of the nipples of the breast by a nursing infant triggers the release of this hormone. Also called posterior pituitary gland. Compare adenohypophysis.
