Psychoneuroendocrine research in depression. II. Hormonal responses to releasing hormones as a probe for hypothalamic-pituitary-endorgan dysfunction.

The rapid growth of fundamental research in neuroendocrinology includes advances in our understanding of the role of neurotransmitters in the control of hypophysiotropic neurons, the concept of neurosecretion, the portal circulation chemotransmitter hypothesis of anterior pituitary regulation, and the chemical structures of the hypophysiotropic hormones. These advances correspond to the emergence of psychoneurobiology, with the appreciation of the roles of neuropeptides, such as hypothalamic releasing and inhibiting hormones, their relevance to brain function and possible involvement in psychiatric disease, and their introduction into psychoneuroendocrinological studies. The subject of the present review is to summarize and integrate current knowledge of the neuroendocrinology of hypothalamic releasing and inhibiting hormones, to apply it to the understanding of the pathogenesis of depression, and to evaluate their relevance as psychoneuroendocrine research tools.