Releasing hormone
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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
*[[Somatostatin]],
*[[Dopamine]].
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 [[Thyroxine|T4]] and [[Triiodothyronine|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.
[[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.
==References==
* Guillemin R. ''Hypothalamic hormones a.k.a. hypothalamic releasing factors.'' J Endocrinol 2005;184:11-28. [http://joe.endocrinology-journals.org/cgi/content/full/184/1/11 Fulltext]. PMID 15642779.
==See also==
*[[Hormone]]
*[[Neuroendocrinology]]
[[Category:Hormones]]
[[Category:Neuroendocrinology]]