In 1990 Dr. Daniel Rudman and his colleagues published in the New England Journal of Medicine a landmark human growth hormone study titled the “Effects of Human Growth Hormone In Men Over 60 Years Old”. This study spurred the interest in growth hormone as a potential treatment to reverse some of the physical changes that occur with aging and has become the landmark human growth hormone study.
Rudman and colleagues hypothesized that the decline in growth hormone and insulin-like growth factor 1 (IGF-1) associated with aging leads to a decrease in body mass and an increase in body fat. They studied 21 men aged 61 to 81 who had IFG-1 levels less than 350 U/l. Twelve men received growth hormone (group 1) and 9 received no treatment (group 2). The study lasted 6 months. IGF-1 levels were measured monthly and lean body mass, fat mass and bone density was measured before and after the study.
With only 21 participants this was a small human growth hormone study.
In practice IGF-1 level are frequently measured rather than growth hormone. Growth hormone has a short-half life meaning is does not stay in blood very long. Plus, it is secreted in pulses. These pulses are random though predictable pulses occurs during deep wave sleep and following intense exercise. But, at other times of the day growth hormone levels can be totally absent. This makes direct measure of growth hormone difficult and interpreting growth hormone levels challenging. But, growth hormone stimulates production of IGF-1 levels which are fairly consistent throughout the day. IGF-1 mediates many of the effects of growth hormone, too.
At the end of the study period IGF-1 levels of those in group 1 rose to youthful levels of 500 to 1500 U/l. IGF-1 levels in group 2 remained below 350 U/l. In group 1 lean body mass increased 8.8 % and body fat decreased 14.4%. Bone density increased 1.6%. No significant change in lean body mass, fat mass, or bone density occurred in group 2.
Small increases in blood pressure and fasting blood sugar were seen in men receiving growth hormone. It should be noted that men receiving growth hormone in this study received doses of growth hormone that are significantly higher than treatment protocols used today. Plus, they received growth hormone 3 times a week. More commonly today growth hormone is prescribed as a daily injection, but in much smaller doses than used in this study. The average weekly dose of growth hormone in Rudman’s was approximately 3 times higher than the weekly dose given today. Most side effects of growth hormone are dose related and are easily managed by reduction in dose.
Many times the improvement in body composition seen in Rudman’s study is downplayed or dismissed by critics of growth hormone use. However, many health problems are related to obesity. Fat is not an inert tissue and has significant adverse effects on body function and metabolism increasing the risk for other diseases. Unfortunately, the significance of muscle loss is also not fully appreciated by many physicians. Loss of muscle leads to a poorer quality of life associated with muscle weakness, loss of mobility, tendency to fall, declining metabolism, and overall loss of function. It would seem that anything that can contribute to fat loss, increase muscle and bone mass, and improve quality of life should receive appropriate attention.