The hypothalamus produces many neurosecretions that are released next to the primary capillary plexus at the median eminence. These hormones enter the long portal system and are carried to their target cells in the adenohypophysis. These hormones can either stimulate or inhibit the release of other hormones from the pituitary gland. The names and actions of the principal hypothalamic releasing and inhibiting hormones are listed below.
Thyrotrophin-releasing Hormone (TRH)
This hormone stimulates the release of Thyrotrophin and Prolactin from the Adenohypophysis.
Gonadotrophin-releasing Hormone (GnRH)
This hormone stimulates the release of Luteinizing hormone (LH) and Follicle-stimulating hormone (FSH) from the Adenohypophysis.
Corticotrophin-releasing Hormone (CRH)
This hormone stimulates the release of Corticotrophin from the Adenohypophysis.
Somatotrophin-releasing Hormone(SRH) or Growth Hormone-releasing Hormone (GHRH)
This hormone stimulates the release of Somatotrophin (Growth Hormone) from the Adenohypophysis.
This hormone inhibits the release of Thyrotrophin and Somatotrophin from the Adenohypophysis.
Antidiuretic Hormone (ADH)/Vasopressin
This hormone inhibits the release of Prolactin from the Adenohypophysis.
There are many other substances released into the primary capillary plexus from the neurones including natriuretic peptide, angiotensin II and enkephalins. The precise role of these substances is still to be fully understood, but it is most likely to be regulatory.