L-dopa is not an artificial human-created drug. It is a natural amino acid derivative that occurs in food, (making up 13% of the velvet bean) and is normally present in the human brain.
L-dopa is the precursor for the neurotransmitter dopamine (DA) and is produced by the action of the enzyme tyrosine hydroxylase on the amino acid tyrosine DA is the precursor of the brain neurotransmitter noradrenalin.
It has been known for over 30 years that it is an effective stimulant of human growth hormone (HGH) release. In 1970, Boyd and colleagues found that a 500mg oral dose (this dosage is FAR more than what you’ll find in most HGH supplemnets) caused a significant rise in plasma growth hormone.