Brian Alexander, author of "Rapture: How Biotech Became the New Religion", takes a sensible look at the science and use of growth hormone: "Growth hormone stimulates the production of insulin growth factor 1, which, in turn, affects everything from sugar-regulating insulin to sex steroids such as testosterone and estrogen. A chart of these hormone interactions looks like a map of the London Underground drawn by MC Escher. And as with that massive subway, one train at one stop can wreak havoc with the whole system. ... The right word is 'overwhelming.' It is extremely complex. ... Researchers still know little about the influence of supplemental growth hormone on cancer cells, diabetes and other diseases ... Life extension can be achieved in lab animals, and research being conducted on mice and monkeys will probably pay off for humans someday. But so far, [studies] show that restoring growth hormone to old animals actually shortens, not lengthens, their life spans."