releasing factor
American Heritage Dictionary:
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re·leas·ing factor
(rĭ-lē'sĭng)
n.
Any of several hormones secreted by the hypothalamus that stimulate the anterior part of the pituitary gland to release certain hormones.
n.
Any of several hormones secreted by the hypothalamus that stimulate the anterior part of the pituitary gland to release certain hormones.
Oxford Dictionary of Sports Science & Medicine:
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releasing factors
A chemical factor secreted by the hypothalamus and transported to the anterior pituitary gland, where it stimulates the secretion of a particular pituitary hormone. For example, growth-hormone-releasing-factor from the hypothalamus stimulates the secretion of human growth hormone.
American Heritage Stedman's Medical Dictionary:
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re·leas·ing factor
(rĭ-le'sĭng)
n. (Abbr. RF)
n. (Abbr. RF)
A substance of hypothalamic origin capable of accelerating the secretion of a given hormone by the anterior lobe of pituitary gland. Also called releasing hormone.
Oxford Dictionary of Biochemistry:
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releasing hormone
or releasing factor
any neuropeptide synthesized in the hypothalamus that is carried to the anterior pituitary where it regulates the production and secretion of the tropic hormones, e.g. thyrotropin, somatotropin, or the gonadotropins. In the anterior pituitary releasing hormones act via the adenylate cyclase system and are then degraded by proteolysis.
any neuropeptide synthesized in the hypothalamus that is carried to the anterior pituitary where it regulates the production and secretion of the tropic hormones, e.g. thyrotropin, somatotropin, or the gonadotropins. In the anterior pituitary releasing hormones act via the adenylate cyclase system and are then degraded by proteolysis.
| release-inhibiting factor, release factor, relaxin-like factor | |
| rem, remnant, remnant hyperlipidemia |
Wikipedia on Answers.com:
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Releasing hormone
Not to be confused with Release factor.
A releasing hormone or releasing factor is a hormone whose main purpose is to control the release of another hormone. The main releasing hormones secreted by the hypothalamus are:
- Thyrotropin-releasing hormone (TRH),
- Corticotropin-releasing hormone (CRH),
- Gonadotropin-releasing hormone (GnRH),
- Growth hormone-releasing hormone (GHRH),
Two other factors are also classed as releasing hormones, although they in fact inhibit pituitary hormone release
For example, TRH is released from the hypothalamus in response to low levels of secretion of thyroid stimulating hormone (TSH) from the pituitary gland. The TSH in turn is under feedback control by the thyroid hormones T4 and T3. When the levels of TSH are too high, they feed back on the brain to shut down the secretion of TRH. Synthetic TRH is also used by physicians as a test of TSH reserve in the pituitary gland as it should stimulate the release of TSH and prolactin from this gland.
Releasing hormones are sometimes known as liberins. For example, TRH may be known as thyroliberin. Inhibiting hormones may be known as statins. For example, dopamine (which inhibits prolactin release) may be called prolactostatin.
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Mechanism
Releasing hormones increase (or, in case of inhibitory factors, decrease) the intracellular concentration of calcium (Ca2+), resulting in vesicle fusion of the respective primary hormone.
For GnRH, TRH and GHRH the increase in Ca2+ is achieved by the releasing hormone coupling and activating G protein coupled receptors coupled to the Gq alpha subunit, activating the IP3/DAG pathway to increase Ca2+.[1] For GHRH, however, this is a minor pathway, the main one being the cAMP dependent pathway. [2]
Notable researchers
Roger Guillemin and Andrew W. Schally were awarded the Nobel Prize in Physiology and Medicine in 1977 for their contributions to understanding "the peptide hormone production of the brain"; these scientists independently first isolated TRH and GnRH and then identified their structures.[3]
See also
References
- ^ Page 237 in: Costanzo, Linda S. (2007). Physiology. Hagerstwon, MD: Lippincott Williams & Wilkins. ISBN 0-7817-7311-3.
- ^ Walter F., PhD. Boron (2003). Medical Physiology: A Cellular And Molecular Approaoch. Elsevier/Saunders. pp. 1300. ISBN 1-4160-2328-3.
- ^ Guillemin R. Hypothalamic hormones a.k.a. hypothalamic releasing factors. J Endocrinol 2005;184:11-28. Fulltext. doi:10.1677/joe.1.05883 PMID 15642779.
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American Heritage Dictionary
The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.
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Oxford Dictionary of Sports Science & Medicine
The Oxford Dictionary of Sports Science & Medicine. Copyright © Michael Kent 1998, 2006, 2007. All rights reserved.
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American Heritage Stedman's Medical Dictionary
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company.
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Oxford Dictionary of Biochemistry
Oxford University Press. Oxford Dictionary of Biochemistry and Molecular Biology © 1997, 2000, 2006 All rights reserved.
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