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Insulin-like growth factor I (IGF-I), one of the body`s many growth factors, is an IGF I 1 Canadian Academy of Sports Nutrition caasnessential element for normal growth and development. Insulin-like growth factors are substances that promote growth in the muscles. They include IGF-I and IGF-II. IGF-I is also called somatomedian-C (Sm-C). Three somatomedians were named somatomedian A, B, and C. Because of similarity and relationship between Sm-C and IGF-II, Sm-C was named IGF-I; but IGF-II is not a somatomedian.

Produced mostly by the liver, IGF-I is a compound that mediates the effects of growth hormone. Indirect effects of GH are attributed to IGF-I. It is IGF-I, not GH itself, that promotes growth and development, meaning that growth hormone works through IGF-I. Thus, IGF-I injections have the same impact as GH.

The two hormones that can elevate the level of IGF-I are growth hormone and dehydroepiandrosterone (DHEA). DHEA is a powerful immune enhancer in its own right. Acting like insulin, IGF-I can improve glucose metabolism and lower blood sugar profiles in patients with type II diabetes. Studies of the use of acute intravenous IGF-I have shown a glucose-lowering protein- sparing effect in adult men.

IGF-I regulates the anabolic effects of GH. It goes to the muscles and ligaments where it develops lean tissue. By traveling to the fat cells, IGF-I burns fat. Subsequently, it increases lean body mass and decreases fat—the two most wanted effects by athletes, particularly bodybuilders. This is the reason that some experts believe that IGF-I is possibly the most potent bodybuilding drug. The ability of IGF-I to help repair peripheral nerve tissue damaged by injury or illness is under extensive investigation.

Because growth hormone secretes in bursts and is rapidly removed by the liver and other tissues, it is medically difficult to measure its level accurately. However, the level of IGF-I is relatively stable. So IGF-I is measured as a screening test for GH deficiency. Furthermore, IGF-I is a good marker of excessive secretion of GH and its level is high almost in all cases. Low level of IGF-I indicates GH deficiency, which requires more medical tests.

Athletes and IGF-I:

Athletes are always looking for the best sports performance- increasing supplements IGF I 2 Canadian Academy of Sports Nutrition caasnand IGF-I is one of them. By taking it directly, athletes bypass many things.

The muscle-building activity of a drug or compound is enough reason for athletes to rush to use it. For athletes, particularly bodybuilders, the mystique of IGF-I is due to its ability to build and define lean muscle and burn fat. Some athletes believe that while using GH may have dangerous side effects, they take high dosage of IGF-I instead. They are wrong! Either GH or IGF-I can cause devastating side effects. Uncontrolled using GH and IGF-I is twisting the lion`s tail. That IGF-I is safer than synthetic GH is not true. Recently, users of IGF-I have increased, because they think if they use IGF-I instead of GH, they can reach to their desired results by bypassing the side effects. But it is jumping out of the frying pan and into the fire.

Since growth hormone levels increase at night and IGF-I levels increase during the day, athletes especially the bodybuilders hope that taking the two together will double the impact on anabolism and decreasing protein break down. But it is not clear whether the hormones have a synergistic effect or not.

Most of the athletes who seek the synthetic IGF-I cannot obtain it and the synthetic IGF-I is very expensive to provide. The prime natural source of IGF-I is colostrum, a most often missed, but potent sports dietary supplement. For detailed information about colostrum, see "Colostrum".

Based upon studies, the dosages of IGF-I vary from 10 to 100 micrograms per day. Athletes are claiming the higher the dosage, the better the results; but there is no controlled studies to support the athletes` claim. Different studies on IGF-I indicate that it must be administered by injection to be effective. It must be injected under the skin.

Does IGF-I have side effects? The answer is yes; they are like those of GH. As we talked earlier, the higher the level of IGF-I, the greater the possibility of side effects occurring. Therefore, we recommend erring on the side of caution.