IGF-1 versus GH/HGH

“GH actually is a precursor to IGF-1. GH does not directly cause muscle growth, but indirectly causes muscle growth by signaling the release of IGF-1. [55] There are several theories as to how GH affects muscle growth. One is called the Dual Effectory Theory, which states that GH has direct anabolic effects on different tissues of the body. [56] In one study involving genetically altered mice, GH has been shown to have more growth potential than 1GF-1, but when an element that destroys IGF-1 was administered together with GH, the anabolic effects weren’t present. [57] This shows that IGF-1 is involved somewhere between the pituitary gland and the target tissue.

A second theory is the Somatomedin theory. This states that GH exerts its anabolic effects through IGF-1. [58] When GH is first released into the bloodstream, it travels to the liver and other surrounding tissues where it begins the synthesis and release of IGF-1. A study performed to support this theory showed that GH-deficient animals were able to reach normal growth levels after IGF-1 administration. [59]

It is a well-known fact that the levels of IGF-1 are significantly raised after GH administration. It would seem logical that one could skip GH administration and take IGF-1 instead as IGF-1 is considered as a potential promoter of growth and lipolysis (lipid breakdown). [60] Due to the lower cost of IGF-1, many have opted to replace GH supplementation with IGF-1. Skipping the sequences involved with synthesizing IGF-1 from GH will yield results that are equal or greater than GH administration. “