TweetBy Bryan Hay****
To understand how IGF-1 works you have to understand how muscles grow. The ability of muscle tissue to constantly regenerate in response to activity makes it unique. Itís ability to respond to physical/mechanical stimuli depends greatly on what are called satellite cells. Satellite cells are muscle precursor cells. You might think of them as "pro-muscle" cells. They are cells that reside on and around muscle cells. These cells sit dormant until called upon by growth factors such as IGF-1. Once this happens these cells divide and genetically change into cells that have nuclei identical to those of muscle cells. These new satellite cells with muscle nuclei are critical if not mandatory to muscle growth.
Without the ability to increase the number of nuclei, a muscle cell will not grow larger and its ability to repair itself is limited. The explanation for this is quite simple. The nucleus of the cell is where all of the blue prints for new muscle come from. The larger the muscle, the more nuclei you need to maintain it. In fact there is a "nuclear to volume" ratio that cannot be overridden. Whenever a muscle grows in response to functional overload there is a positive correlation between the increase in the number of myonuclei and the increase in fiber cross sectional area (CSA). When satellite cells are prohibited from donating new nuclei, overloaded muscle will not grow (Rosenblatt,1992 & 1994; Phelan,1997). So you see, one important key to unnatural muscle growth is the activation of satellite cells by growth factors such as IGF-1.
IGF-1 stimulates both proliferation (an increase in cell number) and differentiation (a conversion to muscle specific nuclei) in an autocrine-paracrine manner, although it induces differentiation to a much greater degree. This is in agreement with the Dual Effector theory. In fact, you can inject a muscle with IGF-1 and it will grow! Studies have shown that , when injected locally, IGF-1 increases satellite cell activity, muscle DNA content, muscle protein content, muscle weight and muscle cross sectional area (Adams,1998).
On the very cutting edge of research scientists are now discovering the signaling pathway by which mechanical stimulation and IGF-1 activity leads to all of the above changes in satellite cells, muscle DNA content, muscle protein content, muscle weight and muscle cross sectional area just outlined above. This research is stemming from studies done to explain cardiac hypertrophy. It involves a muscle enzyme called calcineurin which is a phosphatase enzyme activated by high intracellular calcium ion concentrations (Dunn, 1999). Note that overloaded muscle is characterized by chronically elevated intracellular calcium ion concentrations. Other recent research has demonstrated that IGF-1 increases intracellular calcium ion concentrations leading to the activation of the signaling pathway, and subsequent muscle fiber hypertrophy (Semsarian, 1999; Musaro, 1999). I am by no means a geneticist so I hesitated even bringing this new research up. In summary the researchers involved in these studies have explained it this way, IGF-1 as well as activated calcineurin, induces expression of the transcription factor GATA-2, which accumulates in a subset of myocyte nuclei, where it associates with calcineurin and a specific dephosphorylated isoform of the transcription factor nuclear factor of activated T cells or NF-ATc1. Thus, IGF-1 induces calcineurin-mediated signaling and activation of GATA-2, a marker of skeletal muscle hypertrophy, which cooperates with selected NF-ATc isoforms to activate gene expression programs leading to increased contractile protein synthesis and muscle hypertrophy. Did you get all that?
By Author Unkown
IGF stands for insulin-like growth factor. It is a natural substance that is produced in the human body and is at its highest natural levels during puberty. During puberty IGF is the most responsible for the natural muscle growth that occurs during these few years. There are many different things that IGF does in the human body; I will only mention the points that would be important for physical enhancement. Among the effects the most positive are increased amino acid transport to cells, increased glucose transport, increased protein synthesis, decreased protein degradation, and increased RNA synthesis.
When IGF is active it behaves differently in different types of tissues. In muscle cells proteins and associated cell components are stimulated. Protein synthesis is increased along with amino acid absorption. As a source of energy, IGF mobilizes fat for use as energy in adipose tissue. In lean tissue,
IGF prevents insulin from transporting glucose across cell membranes. As a result the cells have to switch to burning off fat as a source of energy.
IGF also mimic's insulin in the human body. It makes muscles more sensitive to insulin's effects, so if you are a person that currently uses insulin you can lower your dosage by a decent margin to achieve the same effects, and as mentioned IGF will keep the insulin from making you fat.
Perhaps the most interesting and potent effect IGF has on the human body is its ability to cause hyperplasia, which is an actual splitting of cells. Hypertrophy is what occurs during weight training and steroid use, it is simply an increase in the size of muscle cells. See, after puberty you have a set number of muscle cells, and all you are able to do is increase the size of these muscle cells, you don't actually gain more. But, with IGF use you are able to cause this hyperplasia which actually increases the number of muscle cells present in the tissue, and through weight training and steroid usage you are able to mature these new cells, in other words make them grow and become stronger. So in a way IGF can actually change your genetic capabilities in terms of muscle tissue and cell count. IGF proliferates and differentiates the number of types of cells present. At a genetic level it has the potential to alter an individuals capacity to build superior muscle density and size.
There is a lot of talk about the similarity between IGF and growth hormone. The most often asked question is simply which is more effective. GH doesn't directly cause your muscles to grow, it works very indirectly by increasing protein synthesis capabilities, increasing the amount of insulin a person can use effectively, and increasing the amount of anabolic steroids a person can use effectively. GH also indirectly causes muscle growth by stimulating the release of IGF when it (the GH) is destroyed in the human body. So one way you could look at it as GH being a precursor to IGF. So to put it simple IGF is more effective at directly causing muscle growth and density increases. IGF is also much more cost effective.
IGF can also be effectively used by itself and gains will still be easily noticeable. With growth hormone you need to use high amounts of anabolics and often insulin to see any gains at all, this is not the case with IGF. IGF can be used by itself and is often used by bodybuilders who bridge between cycles, during this bridge is a good time to use IGF since it has no effect on natural testosterone production so it will therefore allow you to return to normal in terms of hormone levels. A stack of IGF, PGF2a, HCG, and clomid would be a good bridge stack and would allow your body to return to normal and still allow you to retain and make new gains.
IGF is a research drug, it hasn't been approved by the FDA for use as a pharmaceutical and it is currently being researched for nerve tissue repair, possible burn victims, and also as a possible aid in muscle wasting for AIDS patients. There are many different analogs of IGF available, instead of mentioning them all, I will simply mention the two most common and the most effective. Regular recombinant IGF is one of the two, it is also the more expensive and the least effective. Regular IGF only has a half-life of about 10-20 minutes in the human body and is quickly destroyed, it can be combined with certain binding proteins to extend the half-life, but it is not a very simple procedure and there is a more effective and less expensive version available. The most effective form of IGF is Long R3 IGF-1, it has been chemically altered and has had amino acid changes which cause it to avoid binding to proteins in the human body and allow it to have a much longer half life, around 20-30 hours. "Long R3 IGF-1 is an 83 amino acid analog of IGF-1 comprising the complete human IGF-1 sequence with the substition of an Arg(R) for the Glu(E) at position three, hence R3, and a 13 amino acid extension peptide at the N terminus. This analog of IGF-1 has been produced with the purpose of increasing the biological activity of the IGF peptide."
"Long R3 IGF-1 is signifacantly more potent than IGF-1. The enhanced potency is due to the decreased binding of Long R3 IGF-1 to all known IGF binding proteins. These binding proteins normally inhibit the biological actions of IGF's."
It is also not as expensive since a media grade version is available which is sufficient for bodybuilding use. There is also a receptor grade available but it is VERY expensive and the only noticeable difference between the two would only be able to be noticed in a laboratory setting. The price on the black market for Long R3 IGF-1 can be seen anywhere from $200-$500 per milligram depending on the source.
The most effective length for a cycle of IGF is 50 days on and 20-40 days off. The most controversy surrounding Long R3 IGF-1 is the effective dosage. The most used dosages range between 20mcg/day to 120+mcg/day. IGF is only available by the milligram, one mg will give you a 50 day cycle at 20mcg/day, 2mg will give you a 50 day cycle at 40mcg/day, 3mg will give you a 50 day cycle at 60mcg/day, 4mg will give you a 50 day cycle at 80mcg/day and so on. The dosage issue mainly revolves around how much money you have to spend, plenty of people use the minimum dosage of 20mcg/day and are happy with the results, and in fact several top bodybuilders use the 20mcg/day dosage and are pleased with the results. IGF is most effective when administered subcutaneously and injected once or twice daily at your current dosage. The best time for injections is either in the morning and/or immediately after weight training.
Another frequently asked question of IGF refers to the real world results, in terms of pure weight gain don't expect to gain 5 lbs. a week like you may off of anadrol or a similar steroid. The only weight you will gain from IGF use is pure lean muscle tissue, with steroids most of the weight gained is water weight. With an effective dosage you can expect to gain 1-2 lbs of new lean muscle tissue every 2-3 weeks and these effects can be increased with the use of testosterone, anabolic steroids, and insulin use. Increased vascularity is also very common, people report seeing veins appear where they never have before. And yet another effect reported is the ability to stay lean while bulking with heavy dosages of steroids and TONS of food while on an IGF cycle, this is perhaps the most pleasing effect. Increased pumps are also noticeable almost immediately, the pumps can almost become painful, pumps are even noticeable when doing cardio.
Overall, IGF is a very exciting drug due to its ability to alter ones genetic capabilities. If you can find a trustworthy source and you use it correctly it can be a VERY useful tool in your bodybuilding drug arsenal.