IGF stands for insulin-like growth factor. It is a natural substance that is produced in the human body and is at its highest natural levels during puberty. During puberty IGF is the most responsible for the natural muscle growth that occurs during these few years.

IGF stands for insulin-like growth factor. It is a natural substance that is produced in the human body and is at its highest natural levels during puberty. During puberty IGF is the most responsible for the natural muscle growth that occurs during these few years.