Hormone Response To Exercise: HGH

By Shelby Stoner, PHASE IV Exercise Physiologist

Other articles in the Hormone Series:

Hormone Response To Exercise: Insulin

Hormone Response To Exercise: Cortisol

Hormone Response To Exercise: Ghrelin

Hormone Response to Exercise: Leptin

Human Growth Hormone, also known as HGH or simply GH, is well known for its anabolic properties including cell growth and regeneration. In order to increase muscle mass, bone density, or simply lean out, we MUST have Human Growth Hormone present. GH is naturally produced in the body in the anterior pituitary gland and once secreted; it remains active for only a few minutes, giving the liver enough time to convert it into growth factors such as insulin-like growth factor-1, or IGF-1 which enhances the anabolic properties of GH.

Like all hormones, GH works with specific receptor sites and can produce a number of responses, including increasing muscle protein synthesis responsible for muscle growth, increasing bone mineralization, supporting immune system function and supporting fat metabolism. In addition, it plays a major role in maintaining the health of vital organs including the brain. The profound effects of GH on tissue health provoked scientists to begin harvesting GH from the pituitary glands of cadavers in the 1950’s, but didn’t synthesize the first GH in labs until 1981. Since then, Growth Hormone has gained popularity as a performance-enhancing substance, especially in young athletes and bodybuilders.

Research in GH supplementation has shown some beneficial effects of GH supplementation related to body composition and metabolism. These studies showed that rhGH (recombinant hGH) treatment for a period of four to six months had favorable effects on body composition, exercise aptitude, renal and cardiac function, and led to an overall improvement in quality of life. HOWEVER, what many people do not realize is that these effects are primarily seen in those who are naturally GH deficient. Although growth hormone has many benefits for those who are congenitally deficient, it does not seem to hold similar promise for healthy athletes. Currently, there is no conclusive evidence that growth hormone enhances athletic performance.

Even without proven performance benefits, this drug has several qualities that attracts athletes. One is that GH causes perceptible fluid shifts within bodily tissues with early use, which causes individuals to feel as if the supplement is working. Growth hormone also has a repartitioning effect which decreases subcutaneous fat, making it more attractive to individuals who are aiming for improved aesthetic appearance. In addition, GH use is appealing to strength and power athletes including bodybuilders because of the uptake of amino acids and muscle protein synthesis while enhancing fat breakdown.

While GH therapy has resulted in increased use of fat for fuel during rest, this improvement has NOT been observed during exercise. Fat availability can affect free fatty acid uptake at rest and during low-intensity exercise, but exercise intensity remains the predominant determinant of substrate selection and can override other influences, especially at high rates of work output. Although growth hormone is reportedly used to enhance athletic performance and has been called the “most anabolic substance known,” its efficacy for the purpose is not well established. Some have suggested that GH is a “wonder drug” that results in “ripped muscle” and provides “stamina increasing properties” even though these strength-enhancing properties in healthy adults have since been proven to be extremely exaggerated. The use of GH in sport today is not just based on its anabolic properties, but also its effect on carbohydrate and fat metabolism. Not only is the anabolic effect of GH favored by high power output athletes, it is now gaining acceptance in endurance sport in combination with methods for enhancing oxygen transport. Studies on endurance athletes have shown that when supplementing GH, exercising lactates were significantly higher than those receiving a placebo which is actually associated with decreased exercise stamina and physical exhaustion. It is not clear how GH treatment increases exercising lactate levels, but it may be associated with increased action of uncoupling proteins in mitochondria or selective inhibition of pyruvate dehydrogenase.

These findings warrant further research because it suggests that endurance athletes using growth hormone may actually be harming their athletic performance. Although there are anecdotal reports on the proclaimed “dramatic increases” in muscle mass and strength after large doses of GH (especially in bodybuilders) their effectiveness under controlled conditions is generally less impressive.

Unfortunately, the use of GH and other performance-enhancing substances is one of the most serious ethical issues facing sport today. A key factor to consider when evaluating GH use in sport is the fact that athletes who take growth hormone often combine use with other anabolic steroids. The postulated mechanism behind GH in athletes includes enhanced amino acid and glucose uptake in skeletal muscle, thus stimulating protein synthesis in combination with increase of free fatty acid mobilization as an energy source. All in all, claims that growth hormone enhances physical performance are not supported by current scientific literature. Although GH may alter body composition, it has minimal effect on key athletic performance outcomes and may even be associated with worsened exercise capacity.

Whether your goals are related to weight loss or improved performance, PHASE IV science has the answers. Call us to schedule a complimentary 30-minute health and fitness consultation at our facility in Santa Monica. 310-582-8212

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