In humans and other animals, growth hormone (GH) stimulates growth, cell reproduction and cell regeneration. It is therefore important for human development. Growth hormone is a stress hormone that increases the concentration of glucose and free fatty acids. It also promotes the production of IGF-1. The most common disease associated with excess growth hormone is pituitary tumor. The effects produced by growth hormone deficiency vary by age. In children, growth arrest and short stature are the main manifestations of growth hormone deficiency, usually due to genetic factors and congenital malformations. It can also lead to delayed sexual maturation. In adults, growth hormone deficiency is rare, the most common cause being pituitary tumors, while other causes include a continuation of childhood growth hormone deficiency, other structural injuries or trauma, and, very rarely, idiopathic growth hormone deficiency (GHD).