HGH, which stands for Human Growth Hormone, is a protein hormone which stimulates growth and cell reproduction in humans. The hormone is produced naturally in the human body, but as it ages, the production slows down. Right now there are HGH products on the market available only by prescription. They are prescribed to adults with true growth hormone deficiency — not the expected decline in growth hormone due to aging. Also to children with illnesses such as kidney failure, short stature, and muscle issues associated with HIV or AIDS. Injections of HGH can increase bone density, muscle mass, and increase exercise capacity. There can be risks associated with taking the hormone unnecessarily, so it is very important to have the doctor's strong recommendation.