by Anthony Roberts
Growth hormone, although it’s been making more headlines today than ever before, is not a new drug – it was first described in the 1920′s and within a few decades, isolated as somatotropin. By 1956, it had been established to increase nitrogen retention in humans (Lancet 1958; 1: 720–1.), an undisputed marker of the anabolic process.
Growth hormone is a protein-based 191-amino acid single-chain polypeptide hormone secreted by somatotroph cells found in the lateral wings of the anterior pituitary gland, under hyperthalamic. It’s function is to stimulate cellular growth and reproduction, and is secreted in greater amounts earlier in life, declines sharply by the 20s, and continues to decline throughout life. Specifically, the term Somatotropin refers to naturally occuring growth hormone 1 (“growth hormone one“), also known as hGH, and Somatropin refers to growth hormone produced by recombinant DNA technology, known as rhGH. In other words, the stuff that comes in vials, and is injected by athletes and bodybuilders is technically rhGH, but the terms GH and hGH, and even rhGH are often used interchangeably in the media. Because rhGH and hGH are identical down to the molecular level, detection of exogenous (outside) use of rhGH by chemical distinction is impossible.
However, recombinant DNA (rDNA) molecules are synthesized through molecular cloning, but appear identical (in your body) to the molecule they’re replicating. The molecules from all organisms share the same chemical structure, but with differing nucleotide sequences. Think of these molecules like a paragraph from your favorite book . You could, theoretically, take another book and cut out various words and letters, and ultimately recreate a verbatim copy of that paragraph. That’s kind of how rDNA cloning works, and it’s how we arrive at end products like rhGH. When your body reads the paragraph, it reads it the same way you would have read the original paragraph from the book it was taken.
Growth hormone deficiency manifests in children as a variety of growth disorders and in adults as adult growth hormone deficiency. Currently, the treatment of these disorders is the only legal use for growth hormone in the United States. But athletes and bodybuilders have been using it for decades to increase strength & lean body mass, while decreasing body fat.
But only recently has the scientific community has recognized the fact that they have been woefully behind the times when it comes to identifying anabolic agents:
GH was recommended in “The Underground Steroid Handbook” in 1983 as “a new and exiting anabolic agent” approximately 7 yr before any publication suggesting that this effect occurred in adults appeared in the scientific literature. – Gibney et. al, Endocrinology Review. 2007 Oct;28(6):603-24.
The 1984 Olympics were known in the underground athletic community as “The Growth Hormone Games” because they not only featured numerous athletes who were rumored to have been using the drug, but also because the games were held in Los Angeles, a Mecca of body-conscious athletes and actors, punctuated by Venice Beach, the epicenter of 1980′s performance enhancing drug use, and the birthplace not only or Arnold, but also of The Underground Steroid Handbook, The Anabolic Reference Guide, and the entire steroid subculture. To say that performance enhancing drugs were readily available to the athletes attending the ’84 Olympics, would be a vast understatement. And Growth Hormone was becoming the drug of choice for some high-profile football players in the area, and spreading like wildfire.
The anabolic (muscle building) effects of growth hormone are generally thought to be in its ability to increase circulating insulin-like growth factor 1 (IGF-I), which is primarily of hepatic (liver-derived) origin, but is also expressed in muscle as a direct result of mechanical stress (i.e. weight training). Growth hormone also causes the synthesis of IGF-I in most non-hepatic (*muscular) tissues, which is also thought to be a major contributor to its anabolic effect.
IGF-1 has been conclusively proven to increase muscle size and strength while decreasing body fat. Of this, there is no lingering question in the scientific commnity. Insulin-like growth factor-I has a profound anabolic effect on protein metabolism; it inhibits whole body protein breakdown and simultaneously stimulates protein synthesis (PMID: 8074213). IGF-1 use is typically cited as one of the major anabolics being used by top bodybuilders, and among top competitors, is considered a must-have compound for competition at the highest levels.
Although anti-doping officials denied that growth hormone did anything to enhance athletic performance, they quickly banned the substance. It wasn’t until a 1990 study published in the New England Journal of Medicine (N Engl J Med 1990; 323:1-6) that growth hormone entered the public consciousness. Table four, in that study, revealed the increases in muscle tissue and concomitant decreases in fat, experienced by elderly men taking the drug:
Still, as was the case with anabolic steroids, scientists denied that the drug could improve athletic performance. This led to a rapid deterioration of scientific credibility within the athletic and bodybuilding community, similar to what was seen with anabolic steroids (which the Physicians Desk Reference still fails to acknowledge will enhance athletic ability).
A Stanford University metastudy, published in the Annals of Internal Medicine (PMID: 18347346) attempted to figure out if growth hormone could improve performance. They analyzed previously published studies comparing participants receiving the hormone to those who didn’t; 27 studies involving 440 participants were examined. The researchers concluded, apparently not understanding that muscle is good for athletes, that growth hormone use may hinder performance:
Claims that growth hormone enhances physical performance are not supported by the scientific literature. Although the limited available evidence suggests that growth hormone increases lean body mass, it may not improve strength; in addition, it may worsen exercise capacity and increase adverse events. More research is needed to conclusively determine the effects of growth hormone on athletic performance.
Later, speaking to MSNBC, the lead researcher repeated her absurd claims: “It doesn’t look like it helps and there’s a hint of evidence it may worsen athletic performance,” said Dr. Hau Liu,
However, in 2010, in the Annals of Internal Medicine (May 4, 2010, Vol. 152 no. 9 568-577) Growth Hormone administration was conclusively shown to increase athletic performance in sprinters, who got substantially faster in their 100m times:
“…significantly reduced fat mass, increased lean body mass[and] significantly increased sprint capacity…”
Growth Hormone, therefore, was finally validated by WADA as being a genuine performance enhancing drug, after several decades of various scientists saying it may increase muscle and burn fat, but do nothing for performance (hint: a more muscular, less fat, first baseman, running back or shot putter, or whatever, is a better than a less muscular more fat version). In metabolic terms, GH use causes a marked increase in lipolysis (fat burning) and Free Fatty Acid levels. After a meal, GH effects protein metabolism, causing increased protein synthesis and decreased whole-body and local-muscular protein breakdown, while decreasing the rate of amino acid oxidation, and activating the mTOR pathway of anabolism (PMID: 19773097). It also prevents carbohydrates from being taken into fat tissue (PMID: 19800274), potentially becauseGH preferentially down-regulates the glucose transporter in adipose tissue. Growth Hormone administration also has beneficial effects on tendon and joint repair (PMID: 21403984).
Dosing strategies vary between athletes and sports, with a low end of 1-2iu/day being used by women or as an adjunct/anabolic enhancer (that takes advantage of GH’s synergy with testosterone). However, 4iu-8iu/day is closer to what we see with athletes and bodybuilders, with a dosing schedule of 1/1 (one day on, one day off), 5/2, or continuous (every day).
But however it’s being used, it has been well established that growth hormone will build muscle and burn fat in athletes, as well as enhance performance.