Human growth hormone (HGH) is a hormone that is naturally produced by the body. It is synthesized and secreted by cells in the anterior pituitary gland located at the base of the brain. Its secretion into the circulation follows a pulsatile pattern resulting in widely fluctuating blood levels that are influenced by multiple factors such as age, gender, sleep, physical activity, diet, stress, fever, steroids and the environment. HGH stimulates many metabolic processes in cells. HGH affects protein, fat, carbohydrate and mineral metabolism. The major role of HGH is to stimulate the liver to secrete Insulin-like Growth Factor-I (IGF-I). IGF-I stimulates production of cartilage cells, resulting in bone growth and also plays a key role in muscle protein synthesis and organ growth.