1. : site into which releasing hormones or inhibiting hormones are secreted 2. : supplies the primary plexus 3. : site that receives the blood and hormones from the primary plexus and into which hormones such as GH, TSH, and ACTH are secreted 4. : blood vessels of the hypophyseal portal system that join two capillary beds 5. : location of synthesis of releasing hormones (RH), such as GHRH, TRH, CRH, and GnRH; or inhibiting hormones (IH), such as GHIH and PIH