HGH, or Human Growth Hormone, is produced in the pea-sized pituitary gland located at the base of the brain. It fuels childhood growth, but by the time we reach middled age, this gland continues to reduce the amount of this hormone it produces.
It helps to regulate such things as bone growth, and sugar and fat metabalism.
Many today tout it as an anti-aging substance and use it in synthetic form. However, there are no studies that confirm the synthetic substitude has any positive effect, and actually, there is quite a list of negative side effects, so it could be quite detrimental.
During fasting, however, we can stimulate our own HGH production naturally.