Production of Pituitary Hormone by Human Pituitary Adenoma is under Autocrine and Paracrine Regulation of Hypothalamic Hormones Secreted from Adenoma Cells

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Two hypotheses, the hypothalamic and pituitary hypotheses, have been suggested concerning the pathogenesis of pituitary adenoma. The recent demonstration of the monoclonality of most human pituitary adenomas has led to wider acceptance of the pituitary hypothesis, which suggests that pituitary adenoma results from monoclonal expansion of a single adenohypophyseal cell with subcellular abnormalities. Meanwhile, the role of hypothalamic hormones in the development of pituitary adenoma has recently attracted the attention of investigators. The present paper discusses the expression of growth hormone-releasing hormone (GHRH) in somatotroph adenoma, and corticotropin-releasing hormone (CRH) in corticotroph adenoma. Locally generated hypothalamic hormones and expression of associated receptors in human pituitary adenoma cells play significant roles in autocrine/paracrine regulation of pituitary hormone production.