July 1, 2001
This Month’s Featured Article:
Does creatine alter our hormone levels?
Exercise and Anabolic Hormone Release
Exercise, when accompanied by a well-balanced diet and adequate rest, stimulates the release of hormones that promote muscle growth. These are known as anabolic (growth promoting) hormones, and include Testosterone, Insulin, and Growth Hormone. Unbeknownst to most athletes the production of these anabolic hormones is what we strive for when training.
What is Growth Hormone?
Growth Hormone, also known as Somatotropin, is released from a small gland in the base of our brains known as the Anterior Pituitary. Growth Hormone is primarily released while we sleep. Hence, it is often said that we build muscle while sleeping, not exercising. However, Growth Hormone is also released in response to exercise. Therefore, sensible exercise and sufficient rest go hand in hand in building muscle.
I’ll reiterate sensible exercise and plenty of rest are equally important in building muscle. On the other hand, training too aggressively and getting too little sleep can actually impede muscle growth and gives rise to a condition known as Overtraining Syndrome (OTS). OTS is more widespread than most realize. Importantly, consuming alcohol before bed also interferes with the nocturnal release of Growth Hormone and, in this respect, stagnates muscle development.
CAUTION: Those post-training beers may be undermining your progress!
Growth Hormone has both metabolic and growth promoting effects. Growth Hormone spares the use of proteins (amino acids) for fuel, and instead draws from our fat reserves (fatty acids) for energy. Therefore, proteins are preserved and fats are broken down as a result of Growth Hormone. At the same time Growth Hormone stimulates the production of new proteins and augments the uptake of amino acids into muscle cells. The net result is that we build more fat-free muscle mass when Growth Hormone levels are high.
Unfortunately, as we get older our Growth Hormone levels decline. Our Growth Hormone levels peak during adolescence, when we are growing most rapidly. At 40 we produce less than half of the Growth Hormone we did in our 20′s. At 80 we produce only 5% of our youthful Growth Hormone levels! The age-induced decrease in Growth Hormone gives rise to a condition known as Somatopause. Frailty, muscle loss, obesity and disordered sleep typify this condition. Importantly, exercise has been shown to increase Growth Hormone production in the elderly. It can thus be said that exercise keeps us young.
Does Creatine Induce the Release of Growth Hormone?
Since creatine increases our exercise capacity, and exercise increases hormone release, it is expected that creatine should also indirectly increase the amounts of anabolic hormones produced while exercising. Indeed, one recent study has possibly demonstrated this predicted effect. Surprisingly, however, in this study Growth Hormone release was observed in non-exercising subjects after ingesting creatine. In other words, just taking creatine was sufficient to increase Growth Hormone production.
The Study: Six males were given a breakfast of 20 grams of creatine monohydrate dissolved in a half-liter of hot water. They were then told to limit their activity (but not fall asleep!) for the rest of the morning. For six hours their blood was monitored at intervals for the presence of creatine and Growth Hormone. As expected, blood creatine levels rose within minutes of taking creatine monohydrate. Blood Growth Hormone levels, on the other hand, required about 2 hours before rising. This lag indicates that the release of Growth Hormone depends on other cellular events occurring first. Growth Hormone increased on average ~80% over baseline values. Albeit provocative, this finding needs to be viewed with caution until corroborated by other studies.
What are the implications of this study?
This study suggests that creatine may have an anabolic property independent from its ability to increase exercise intensity. This result may also explain why some studies have shown that muscle cells raised in “tissue culture” (out side of the animal in plastic dishes) increase their production of muscle proteins when exposed to creatine. As were the subjects in the previously mentioned study, these muscle cells were inactive due to their growth conditions.
Another unexplained observation is why creatine appears to be less effective in the elderly. This situation may be partially explained by the decline in Growth Hormone levels in the aged. In other words, part of the benefit of creatine might be absent in elderly persons with less Growth Hormone.
Time will tell if these assumptions are right. We’ll just have to wait.
Problems with the Study
Firstly, since these experiments were conducted on a relatively young (~23 years of age) and healthy set of subjects, it is not known whether these findings also apply to the elderly and ill.
Secondly, the sample size was small (six) and the individual responses to creatine varied widely. Three showed strong increases in Growth Hormone levels, two had moderate to low increases in Growth Hormone, and one showed no increase. This variability in Growth Hormone release is somewhat reminiscent of the situation of nonresponders to creatine. In fact, the authors of the study postulated that such differences in Growth Hormone release might underlie creatine-nonresponsiveness.
Finally, the amount of creatine used in the study was comparable to a typical loading dose – taken all at once! This practice is not recommended to the general product.
1. Are other anabolic hormones similarly influenced by creatine?
In this study it was not determined whether other anabolic hormones, such as testosterone or insulin, similarly increase with creatine use.
2. What about Insulin-Like Growth Factor?
Many of the effects of Growth Hormone are mediated by Insulin-Like Growth Factor 1 (IGF-1), which the liver produces when stimulated by Growth Hormone. Interestingly, IGF-1 has also been shown to enhance creatine uptake into isolated muscle cells. Could this work in a feed-forward manner? In other words, does IGF-1-induced creatine uptake, further enhance Growth Hormone release.
3. What is the cellular signal that triggers Growth Hormone release?
Growth Hormone levels increase a few hours after creatine levels do. The biologically active form of creatine is phosphocreatine, creatine to which a phosphate group has been attached. Could phosphocreatine be the signal that triggers the release of creatine from the Anterior Pituitary in our brains?
Creatine enhances exercise performance in most young and healthy individuals. Since exercise induces the release of anabolic hormones, creatine supplementation should also, in theory, indirectly increase the release of Testosterone, Insulin and Growth Hormone during exercise. This study suggests that creatine by itself (in the absence of exercise) may suffice to trigger the release Growth Hormone by the body. This finding is intriguing and might explain the previously unexplained increase in protein synthesis in isolated muscle cells not undergoing activity. Furthermore, if Growth Hormone mediates part of the effect of creatine supplementation, then this study might also explain why creatine supplementation is often less efficacious in the elderly, which have reduced Growth Hormone levels. In conclusion, this study suggests that creatine supplementation may have anabolic properties independent of its effect on energy metabolism. Future scientific investigation will tell if this finding is valid.
Schedel, J.M., Tanaka, H., Kiyonaga, A., Shindo, M. and Schutz, Y. (December 2000) Acute creatine loading enhances growth hormone secretion. The Journal of Sports Medicine and Physical Fitness Volume 40: pages 336-342.
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