Human growth hormone (HGH) is a hormone synthesized and secreted by the pituitary gland, which stimulates growth and cell reproduction in humans and other animals. In 1985, biosynthetic human growth hormone replaced pituitary-derived human growth hormone for therapeutic use in the United States. Biosynthetic human growth hormone, also referred to as recombinant human growth hormone, is also called somatropin and abbreviated as HGH. When used as a medically supervised pharmacological treatment for clinically diagnosed growth hormone deficiency, as diagnosed by an endocrinologist; the usage of HGH injection is recommended to create a healthy balanced endocrinological system.

A deficiency of growth hormone produces significantly different symptoms at various ages. In children, growth failure and short stature are the major manifestations of HGH deficiency. Children can also be affected psychologically in the form of depression, and an overall systemic inefficiency. In adults the effects of deficiency are not as obvious. Symptoms may include, but are not limited to, deficiencies of strength, energy, and bone mass, as well as increased cardiovascular risk.

The effect of HGH generally creates an anabolic reaction, meaning a building up of tissue. While best known for creating an increase in height, it also has been known to strengthen bone, and increase muscle mass through the creation of new muscle cells-which is not the same as hypertrophy (making existing muscles bigger). Growth hormone can decrease adipose (fat) deposits, and stimulate growth in all internal organs including brain tissue. These gains are not without side effects that are associated with changing hormone levels within a healthy system. The gains do not significantly increase muscle strength, or cardiovascular endurance.

A common misconception in the world of athletes is that growth hormone is a miracle substance. In reality, the strength that athletes gain from taking 'performance enhancing drugs, would come from an anabolic steroid rather than from growth hormone. Most athletes who take growth hormone, start out taking it to speed recovery from an injury, and may continue to take it based upon misinformation.

There are non-injectable HGH products (HGH Supplements and HGH Sprays) for people who are uneasy with daily shots.