As the molecules of IGF-1 are carried by binding proteins from the liver to other parts of the body, they attach onto the walls of cells that make up the various organs. From this point on, just how HGH works its magic (in the form of its successor, IGF-1) is not known with absolute certainty. What is known is that IGF-1 with binding protein attaches to cell membrane receptors and stimulates cell differentiation and division, conferring positive effects on cartilage, blood cells, ovarian hormone production, muscle growth and lens differentiation. As well, IGF-1 signals a rejuvenation and restoration in all cells of the body.

Some of the latest research in this area is currently being conducted by Grace Wong of Genentech, where recombinant HGH was first synthesized. Wong theorizes that HGH (in the form of IGF-1) works by intervening in a causal chain in the following way - and here we come back once more to those nasty free radicals.

As our cells produce energy, one of the by-products consists of oxygen based free radicals. In our cells these free radicals in turn activate destructive enzymes called proteases, which attack and damage the protein in our cells.
And when enough damage occurs, the cell dies.

Certain anti-oxidants such as Vitamins E and C are able to nullify some of the action of these free radicals which stimulate the destructive protease activity. But HGH works at the problem closer to its source.

Current research indicates that HGH activates an innate defense mechanism in the cell which brings forth substances called protease inhibitors. These protease inhibitors, as their name suggests, interfere with the destructive activity of proteases. And these protease inhibitors are able to do this even when free radicals are present and "egging" the proteases on.

By way of analogy you might picture this in terms of the automobile. We need the automobile (cellular energy production) and yet the by-product that it gives off, its exhaust (free radicals), is harmful for us to breathe in as we drive along. If we had air filters in our cars that screened out some of the exhaust fumes, that would be somewhat akin to the action of anti-oxidants,which are able to neutralize some of the free radicals and thereby reduce their capacity to activate the destructive proteases.