Human growth hormones last only a few hours in the user's system. The half-life for HGH lasts only 17 to 45 minutes, according to WebMD.
Human Growth Hormone production takes place in the pituitary gland at the center of the brain.The HGH's primary function is cellular growth and regeneration, as cited by growthhormonesprays.com. HGH is secreted more during puberty when teenagers are growing. The secretion also happens during a heavy sleep, after an intense exercise or when one's body is weak in insulin.
HGH supplements have an anti-aging property, help with building muscles, fat reduction and can provide an energy boost. It is also believed to improve bone density.