Thyrotropin releasing hormone (TRH) is a signalling substance that is produced in several organ systems. There it plays an important role in their respective systeomics.
The Tripeptide TRH (pyroGlu-His-ProNH2) has a molecular weight of 362. Its structure has been first described in 1962.
TRH acts as a releasing hormone that is formed by hypothalamic neurons. It is conveyed via the portal vessel system that connects hypothalamus and pituitary gland. In the pituitary it stimulates after being bound to TRHR1-receptors in the contex of the Thyrotropic feedback control secretion of TSH.
Via G-proteins it a delivers a setpoint for the feedback control. Additionaly, formation of TRH is inhibited in the form of degenerative feedback by thyroid hormones.
Hormones and Transmitters that are apt to influence TRH secretion are:
TRH can be found in several areas of central nervous system. More than 2/3 of this central fraction are to be found outside the zone that governs thyrotropic feedback control. Being bound to TRHR1- and TRHR2-recetpors TRH acts here as neurotransmitter or neuromodulator. It plays a central role in body temperature control, in the limbic system, in learning, in sleep, in processing of pain and in sensoric perception.
In the [[Gastrointestinal tract|gastrointestinal tract] TRH has multiple effects, particularly on motility of stomach and intestine and on secretion of Insulin and pancreatic enzymes.
In peripheral blood plasma TRH is found in negligibly low concentration. Its several sites of action are contextually isolated by blood-brain-barrier or the concentration gradient at the end of the portal vessel system between hypothalamus and pituitary and in gastrointestinal tract, respectively. Thus, interactions among its different functions are prevented.
This page was last edited on 29 January 2006, at 00:32.
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