Growth hormone is a special type of protein made in the brain by the pituitary gland. It is responsible for more than just physical growth – it helps our muscles, bones and metabolism. Growth hormone deficiency (GHD) can occur at any age, in both children and adults. GHD results when the pituitary gland does not produce enough growth hormone. In children, GHD may occur during infancy or later in childhood and result in a lack of growth. Most adults are diagnosed with GHD as children and require treatment throughout life; however, it is possible for an adult to acquire GHD later in life, usually through damage to the pituitary or hypothalamus gland. The cause of GHD in children and adults is a poorly formed or damaged pituitary gland or hypothalamus.