It is now indisputably established that a cohort of neurotransmitters and neuropeptides affect the secretion of anterior pituitary hormones by modulating the functional activity of specific hypophysiotropic regulatory hormones. Some salient aspects of the role of gamma-aminobutyric acid in the control of prolactin secretion and of catecholamines and acetylcholine in the control of growth hormone secretion are reviewed, also underlying some diagnostic and therapeutic applications of the new findings in neuroendocrine disorders.