Dopamine-dopamine is also referred to as prolactin inhibiting factor. the vast majorityof hormones produced and secreted by the pituitary are stimulated by an associated releasing factor secreted by the hypothalamus. however, prolactin is under the tonic inhibition by dopamine. as levels of dopamine fall, the lactotrophs in the pituitary respond rapidly by actively secreting more prolactin. all of the currently prescribed galatagogues, such as domperidone, are dopamine antagonists that act to increase prolactin secretion, resulting in increased breast milk production.there is some evidence that trh and a prolactin releasing peptide (prrp) may stimulate the secretion of prolactin. however, both of these compounds at physiological levels do not appear capable of overcoming the tonic inhibition of dopamine. additionally, trh stimulation of prolactin secretion is almost always accompanied by decreased levels of dopamine.