HGH stands for human growth hormone. This chemical is naturally secreted in the brain and it helps determine a person's size. It stimulates bone and tissue growth, the release of other hormones, and it helps determine a person's physical size. Those who don't receive enough human growth hormone may remain permanently small, whereas those who secrete too much may become giants in stature. Human growth hormone is produced mostly when a person is moving from adolescence to young adulthood, and its production goes down with age.
HGH and Age
As the body ages, the percentage of HGH produced goes down. In a 60-year-old man there is perhaps 1/5 as much HGH being produced as there is in a 20-year-old man. In experiments that have been conducted, injecting older men in the range of 70-80 resulted in an increase in lean muscle mass, energy, sexual desire and output. It also showed a marked improvement in other hormones such as testosterone. While not the main effect of HGH, increasing it does increase the amount of testosterone in a male.