GH HAS DIRECT ANABOLIC ACTIONS ON MUSCLE INDEPENDENT OF IGF-1.
“Absorb what is useful, reject what is useless”
– Bruce Lee
“GROWTH HORMONE IS NO MUSCLE BUILDER.” This is headline that appeared in many recent newspapers and newswires this month. The newspapers and media tend to vilify anything that builds muscle, the press has jumped all over a recent meta-analysis (a collection of previous research findings) published in this month’s journal of the Annals of Internal Medicine1 that reported GH has little benefits for building muscle or improving quality of life. The article went on to explain how although growth hormone (GH), which has been reported to build muscle and reduce bodyfat, GH is nothing more than snake-oil! The meta-analysis also noted that GH causes a host of unhealthy side effects, including joint pain, soft tissue swelling, carpal tunnel syndrome, and a heightened risk of diabetes. The article did acknowledge that GH administration did increase lean muscle mass by more than two kilograms (four pounds) and decreased fat mass by roughly the same amount but noted that the side effects associated with GH usage was not worth the small changes in body composition. The lead author also claimed that the small increases in lean mass could easily be accomplished by starting a resistance exercise program. So is GH as worthless for building muscle as the media is portraying it to be? Don’t believe the hype, GH is an important muscle builder. A few days after the GH bashing study was published, Ronald M. Klatz, M.D., President of the American Academy of Anti-Aging Medicine responded to the article with the following,
“The American Academy of Anti-Aging Medicine has reviewed the findings of the meta-analysis concerning adult growth hormone (GH; HGH) replacement therapy published in the January 15, 2007 issue of the Annals of Internal Medicine, and refutes the paper's findings. The meta-analysis is flawed, as it is based on an incomplete compilation of clinical studies of GH replacement in healthy adults. The American Academy of Anti-Aging Medicine submits that thousands of published studies on hundreds of thousands of patients have demonstrated the clear benefits of adult GH replacement therapy, when utilized under proper clinical guidelines and at proper physiological dosages. Real-world results must take precedence over academic hypotheses as to benefits and risks."
GH Works Synergistically With Other Anabolic Hormones
GH has become a very controversial drug over the years in the medical field, but it has become even more controversial among the exercise world in terms of its effect on building muscle. A number of animal studies have shown that GH is not essential for exercise induced muscle hypertrophy; however, this does not mean that GH has no role to play in building muscle. GH works synergistically with other anabolic hormones such as IGF-1 and testosterone. Research with various muscle wasting disorders have shown that a combination of GH and testosterone or GH plus IGF-1, work better than if each is used separately3, 10, 12, 22, 29. Both GH and IGF-1 directly increase whole body protein synthesis, but unlike GH, IGF-1 reduces muscle tissue breakdown31. It is well acknowledged that GH is not as anabolic as testosterone, but GH does play an essential role in the grand scheme of building muscle. Testosterone is the king of building muscle, but testosterone can also increases both GH and IGF-1 levels, mainly thru aromatization of estrogen. Interestingly, if testosterone is administered with an aromatize inhibitor (tamoxifen), there are no increases in GH or IGF-120. It seems overwhelming clear that GH by itself is only a mild anabolic agent at best, but when combined with other anabolics, it’s clear that GH produces an additive effect. For example, Gibney et al.21 compared the effects of GH alone or GH plus testosterone treatment. GH increased IGF-1 levels; however, co-administration of GH and testosterone induced an even greater rise in IGF-1 levels. In another study, researchers examined the effects of GH alone or GH plus testosterone on protein synthesis. GH increased protein synthesis by itself, but a combination of GH and testosterone had an even greater effect on increasing protein synthesis30. One of the pioneers in GH research Bill Kraemer once said at the American College of Sports Medicine that. “GH responses to exercise are essential and more importantly, the anabolic hormone response that occurs with resistance exercise is like a symphony and GH is an important part of that symphony along with testosterone, IGF-1, MGF, and other anabolic hormones.” Think of GH as being the drummer of your band, by itself a drum solo will probably suck, but combine him with the guitar player (IGF-1), and a good singer (testosterone) and you have one kick ass band.
So if GH is as worthless for building muscle as the media portrays it to be, let’s look at some of the research studies examining the anabolic actions of GH. Here are a few highlights of some of the actions in which GH contributes to building muscle by itself and in conjunction with other anabolics:
• One study reported that GH administration results in a reduction in myostatin expression in muscle and resulted in an increase in lean muscle mass. Additionally, when researchers administered pegvisomant, (a drug that blocks the actions of GH binding to its receptor) myostatin protein was significantly increased2.
• GH increases protein synthesis thru the mTOR pathway (an important stimulator of muscle protein synthesis) 33.
• When the effects of GH or a combination of GH and testosterone on lean muscle mass and fat mass were compared, a combination of GH and testosterone resulted in superior increases in lean muscle mass and reduced fat mass compared to GH or testosterone alone. The effects of GH and testosterone on lean body mass appeared additive, suggesting that both GH and testosterone are synergistic yet increase muscle hypertrophy thru different mechanisms3,10.
• MGF (a powerful local growth factor) in skeletal muscle is increased with GH administration4.
• GH has direct actions on skeletal muscle that are independent of IGF-118.
• A single dose of GH has been shown to increase IGF-1 mRNA ( a growth factor) in muscle26
• GH stimulatory effects on muscle protein synthesis may be in part due in part to GH’s direct effects on satellite cells18
• A combination of GH and IGF-1 injections was found to be superior for increasing muscle mass compared to GH or IGF-1 alone12,22.
• Acute and chronic hormonal responses to resistance training were evaluated in 11 college men who completed 12 weeks (33 sessions) of high volume resistance training. Significant correlations existed only between absolute mean GH increases over the training sessions and the degree of muscle fiber hypertrophy for type I and type II fibers7.
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