IGF-1, Insulin-Like Growth Factor 1

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IGF-1, Insulin-Like Growth Factor 1

By Anthony Roberts

Disclaimer: Muscle Evolution does not condone the use of Performance enhancing substances. We choose to rather inform and educate than ignore and avoid publishing information. Always consult a qualified practitioner before embarking on any anabolic or anxillary cycle.

Now that we’ve gone over GH, and mentioned (albeit briefly) IGF-1, we should go into the latter a bit further. IGF-1, also known as somatomedin C, is a polypeptide hormone almost the same size as insulin, or 70 amino acids.

It’s a highly anabolic hormone released primarily in the liver and also in peripheral tissues in response to training. Working with growth hormone, it’s responsible for much what we commonly think is the anabolic activity of GH. This includes some of the things I mentioned previously, including nitrogen retention and protein synthesis (1), muscle cell hyperplasia, and mitogenesis (the growth of new muscle fibres). Although it seems a bit complicated, IGF-1 can also induce skeletal muscle hypertrophy (make your muscles bigger) by activating what is known as the phosphatidylinositol 3-kinase (PI3K)-Akt pathway (2). As you can guess, IGF-1 acts on several different tissues to enhance growth via numerous mechanisms.

The Role of IGF-1 inside the body.

As I mentioned, GH and IGF-1 are intimately related, although they can produce a host of divergent effects. GH and IGF-1 levels are both elevated dramatically following exercise, and it’s been speculated that this may be the reason that lifting heavy stuff is such a great way to pack on muscle mass. In fact, IGF-1 has shown promise in being used as anabolic substitute for GH (3) in certain instances. IGF-1 is also known to be a highly anti-catabolic agent as well (3,4). If you’re considering IGF-1 for anabolic purposes, you need to remember that the anabolic effects of IGF-1 are still limited only by the protein (amino acid) supply within muscle cells (5,6), something that is true for virtually all anabolic agents.

IGF-1 was very interesting to me because I wanted to use it to heal some old injuries to continue playing sports. However, also worthy of note is that fact that I was very interested to learn that IGF-1 can actually improve an athlete’s ability to learn new skills and techniques. This is because IGF-1 is a neuroprotector and neuropromotor (2,7,8). This effect is most likely made possible by the fact that there are IGF-1 receptors within the brain and in motor neurons (9). The most interesting part of IGF-1, however, and the part that made me research it in the first place, is that exogenous IGF-1 administration may improve collagen formation and thereby aid in the repair of cartilage (10-11). IGF-1 is also essential to maintaining healthy bone density and regulating bone density (12). With these qualities in mind, you can see why IGF-1 administration may be highly useful for rehabilitation of any kind of joint injury.

References:

1. Wolf SE, Barrow RE, Herndon DN. Growth hormone and IGF-I

therapy in the hypercatabolic patient. Baillieres Clin

Endocrinol Metab. 1996 Jul;10(3):447-63. Review.

2. Glass DJ. Molecular mechanisms modulating muscle mass.

Trends Mol Med. 2003 Aug;9(8):344-50. Review.

3. Bondy CA, Underwood LE, Clemmons DR, Guler HP, Bach MA,

Skarulis M. Clinical uses of insulin like growth factor I

(IGF-I).Ann Intern Med. 1994 Apr 1;120(7):593-601.

4. Fang CH, Li BG, James JH, King JK, Evenson AR, Warden

GD, Hasselgren PO. Protein breakdown in muscle from burned

rats is blocked by insulin-like growth factor 1 and

glycogen synthase kinase-3beta inhibitors. Endocrinology.

2005 Jul;146(7):3141-9.

5. Murphy MG, Plunkett LM, Gertz BJ, He W, Wittreich J, Polvino WM, Clemmons DR. MK-677, an orally active growth hormone secretagogue, reverses diet-induced catabolism. J Clin Endocrinol Metab. 1998 Feb;83(2):320-5.

6. Fryburg DA, Jahn LA, Hill SA, Oliveras DM, Barrett EJ.

Insulin and insulin-like growth factor-I enhance human

skeletal muscle protein anabolism during hyperaminoacidemia

by different mechanisms. 1995 Oct;96(4):1722-9.

7. Barton-Davis ER, Shoturma DI, Musaro A, Rosenthal N,

Sweeney HL. Viral mediated expression of insulin-like

growth factor I blocks the aging-related loss of skeletal

muscle function. Proc Natl Acad Sci USA. 1998 Dec

22;95(26):15603-7.

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