Growth Hormone (GH):  It is the principle pituitary hormone that regulates growth and metabolism.  Its action is primarily carried out by IGF-1 which is made in the liver.  GH also has direct actions on the blood vessels both extra-cranially and in the brain.  GH is essential for normal growth and development but is also important as an adult for muscle mass, exercise capacity and general quality of life. GH deficiency is treatable by a daily injection of GH.  Learn more.