<P> For example, thyrotropin - releasing hormone (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 . </P> <P> The main releasing hormones are as follows: </P> <Ul> <Li> The hypothalamus uses thyrotropin - releasing hormone (TRH or thyroliberin) to tell the pituitary to release more thyrotropin . </Li> <Li> The hypothalamus uses corticotropin - releasing hormone (CRH or corticoliberin) to tell the pituitary to release more corticotropin . </Li> <Li> The hypothalamus uses gonadotropin - releasing hormone (GnRH or gonadoliberin) to tell the pituitary to release more gonadotropin . </Li> <Li> The hypothalamus uses growth hormone--releasing hormone (GHRH or somatoliberin) to tell the pituitary to release more somatotropin . </Li> </Ul> <Li> The hypothalamus uses thyrotropin - releasing hormone (TRH or thyroliberin) to tell the pituitary to release more thyrotropin . </Li>

What are the releasing hormones from the hypothalamus