Releasing hormone
WordNet
noun
(1) Any of several hormones produced in the hypothalamus and carried by a vein to the anterior pituitary gland where they stimulate the release of anterior pituitary hormones; each of these hormones causes the anterior pituitary to secrete a specific hormone
(2) A substance produced by the hypothalamus that is capable of accelerating the secretion of a given hormone by the anterior pituitary gland