n. the study of the relationships between the nervous system—especially the brain—and the endocrine system. Some cells within the nervous system release hormones into the local or systemic circulation; these are called neuroendocrine (or neurosecretory) cells. The hypothalamus, for example, produces releasing hormones that regulate secretion of pituitary hormones. Certain substances, such as norepinephrine, act both as hormones and as neurotransmitters. See also psychoneuroendocrinology. —neuroendocrinologicaladj.—neuroendocrinologistn.