When the level of TSH is too high, they feed back on the brain to shut down the secretion of TRH.
Such activity is only one of many functions that they have (such as neurotransmitter and receptor antagonist roles), and they are not always called hormones, although many are neuropeptides or neurosteroids.
They include the following: Examples of releasing and inhibiting hormones for exocrine hormones are gastrin-releasing peptide (GRP) and gastric inhibitory polypeptide (GIP), which regulate gastrin production.
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.
[2] 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.