In 1986, the advent of recombinant DNA technology (gene cloning) enabled scientists to produce large quantities of pure, uncontaminated human growth hormone from bacteria. This development set in motion renewed interest in the other physiologic roles of hGH because of its availability for clinical research.

When researchers looked back at records of adults who had been treated with hGH as children or those who had become growth hormone deficient as a result of trauma or tumors, they found that they were not doing very well. They had two times the rate of death from cardiovascular disease compared with age-matched controls; increased abdominal fat; decreased muscle mass and strength; increased fatigue, social isolation and depression; and poor performance at work. These patients appeared to be suffering from premature aging. Bengt Bengtsson, MD and his group in Sweden decided to study the effect of the now more available recombinant hGH on these patients. He found that virtually all of these aspects of premature aging were reversed with one year of treatment, and that they returned to baseline with cessation of therapy. This research led to the FDA approval of hGH replacement therapy in growth hormone deficient adults (GHDA) in August of 1996.

At about the same time, Daniel Rudman, MD, at the University of Wisconsin, was approaching this from a slightly different angle. He had documented the continuous decline in growth hormone secretion beginning in the third decade of life and wondered if it was responsible for the well-known body composition changes associated with aging such as decreased muscle tone, increased abdominal fat, and thinning skin. In 1990, he published a seminal article in The New England Journal of Medicine in which he reported the spectacular age reversing effects of hGH replacement in 21 men between the ages of 61 and 81. After six months of therapy, these men had gained on average 8.8% lean body mass and lost 14% fat mass, predominately around the waist; had increased their skin thickness by 7% (your skin is thicker and more elastic when you’re young); had increased bone density 1.4%; and felt a greater sense of well-being. In the conclusion, Rudman wrote that these changes in body composition are “equivalent in magnitude to the changes incurred during 10 to 20 years of aging.”

The results of this study triggered immense interest in hGH in the treatment of GHDA. The National Institutes on Aging (NIA), a branch of the National Institutes of Health, initiated a number of large clinical trials to test the effect of hormone replacement with hGH and sex steroids on healthy men and women 65 to 88 years old. This is likely because they recognize that fully 40% of adults over 60 have IGF-I levels the same as growth stunted children or individuals suffering from pituitary damage.

When the results were published by Drs Blackman and Harman in 2002, they showed the expected improvements in body composition in men and women (increased muscle and decreased fat), and in strength and VO2 max (aerobic capacity) in men on GH and testosterone (but not in women). Yet these promising results were not heralded as unequivocally positive because of a “high incidence of side effects.” The New York Times ran a story, “Growth Hormone Changed Older Bodies, for Better and Worse,” in which the benefits in body composition were juxtaposed to the side effects. The gist is that the side effects were markedly reduced when the doses were adjusted into the physiological range - those levels normally found in the human body.
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