Growth hormone is a single-chain peptide hormone produced by the pituitary gland. This is the hormone that helps you grow during childhood, hence the word “growth”. GH reaches its peak around the age of 20 and begins to plummet around age 25. Thus, the dreaded aging process begins, as this hormone slowly declines for the rest of your life. Growing isn’t the only thing GH is good for. Many experts say that supplementing growth hormone levels when you are older may help bring them back to levels you had in your 20’s.