There are a number of substances or agents that act as secretogogues. Some of the most effective and most commonly used are amino acids. Amino acids, we will recall, are the building blocks of protein. Of the twenty-one amino acids needed as part of our physiological requirements, nine of them our bodies cannot make on their own, and must have supplied through diet.

The early, ground-breaking work in the field of oral HGH secretogogues was done by Doctors Isadori, Lo Monoco, and Cappa in 1981 at the University of Rome. In the 1990's, because of both their effectiveness and convenient mode of delivery, secretogogues have undergone a flurry of interest and activity. Numerous studies are ongoing and in the months and years to come, there will be a flood of detailed data concerning them. Recently, writing about amino acids in their role as secretogogues, Dr. Chein, in his new book "Age Reversal: From Hormones to Telomeres" stated, "Researchers have isolated specific amino acids that appear to simulate the release of HGH of the pituitary. By taking supplemental amino acids, you can raise your serum (in the blood) levels...."

Many of the amino acids that serve as HGH releasers have a synergistic effect when used in combination. Preparations of secretogogues that contain a number of amino acids are frequently referred to as amino acid stacks, the term "stack" having been borrowed from the weightlifting community, where it was used to signify a number of preparations used in conjunction with one another. The recent ability to produce crystalline free-form amino acids at relatively low cost, has brought about a revolution in secretogogue technology. Many marketed HGH releasers are ineffective.

To be effective HGH releasers, specific combinations and amounts of amino acid salts are required.