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  • ACTHAdrenocorticotropic hormone
  • ANP Atrial natriuretic peptide
  • APUD Amine precursor uptake and decarboxylation (cell)
  • CRHCorticotropin-releasing hormone
  • CT Computed tomography
  • FDG-PET Fluorodeoxyglucose positron emission tomography
  • FGF Fibroblast growth factor
  • FSH Follicle-stimulating hormone
  • GHGrowth hormone
  • GHRH Growth hormone–releasing hormone
  • hCG Human chorionic gonadotropin
  • HTLV-1 Human T cell leukemia virus-I
  • IGF Insulin-like growth factor
  • IGF-BP3 Insulin-like growth factor binding protein-3
  • IL Interleukin
  • LH Luteinizing hormone
  • MEPE Matrix extracellular phosphoglycoprotein
  • MRI Magnetic resonance imaging
  • POMC Proopiomelanocortin
  • PTH Parathyroid hormone
  • PTHrP Parathyroid hormone-related protein
  • SIADH Syndrome of inappropriate antidiuretic hormone (secretion)
  • TNF Tumor necrosis factor
  • VIP Vasoactive intestinal peptide

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Some of the most challenging endocrine problems occur in patients with malignancies of diverse cell types, because both endocrine and nonendocrine tumors secrete polypeptide hormones. As it became recognized that a polypeptide hormone could be produced by tumor cells derived from a tissue that normally did not secrete the hormone, the notion of ectopic hormone production developed. Most tumors associated with ectopic hormone syndromes are derived from cells that are normally capable of producing peptide hormones. Initially, it was thought that ectopic hormone production by tumor cells was a rare event. Interestingly, both the frequency and the original conception of this syndrome have been redefined over the last few decades. It has come to be appreciated—through the use of modern biochemical and molecular biologic techniques—that the synthesis of peptide hormones and the transcription of their genes by tumor cells are in fact quite common occurrences. Tumor cells may differ from normal cells in their ability or inability to process precursor molecules, which may account for the presence or absence of hormone excess states and for the profile of peptide hormone forms and fragments present in the circulation and in tumor cell extracts. However, tumor production of hormone fragments or precursors is much more common than the clinical syndromes of hormone excess.

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The classic criteria used to confirm that a tumor is the source of a hormone excess state include the following: (1) evidence of an endocrinopathy in a patient with a tumor; (2) remission of the endocrinopathy after tumor resection; (3) detection of an arteriovenous gradient across the tumor; and (4) documentation of protein and messenger RNA encoding the hormone being produced by tumor tissue.

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In addition to classic hormone excess states resulting from the ectopic or inappropriate secretion of a hormone by an endocrine or nonendocrine tumor, endocrinopathies can result from the ectopic expression of a hormone's receptor. This is well illustrated, for example, by the occurrence of Cushing syndrome in pregnancy or in relation to meals, due to the ectopic expression of luteinizing hormone (LH) or gastric inhibitory polypeptide receptors in adrenal tissue, respectively. Several other examples of ectopic receptor syndromes have been documented. Some of these will be discussed later, particularly as a cause for unusual forms of adrenocorticotropic hormone (ACTH)-independent Cushing syndrome.

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A variety of peptides are produced by both benign ...

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