The hypothalamus exerts an inhibitory influence on prolactin release from the anterior pituitary. Whether or not peptide hypothalamic prolactin-regulating factors, analogous to those for other pituitary hormones, exist, remains to be confirmed. There is evidence that catecholamines and indolamines directly affect prolactin release. This concept may explain the pathogenesis of galactorrhoea-amenorrhoea and other endocrine diseases produced by hypothalamic-pituitary disorders.