PEG-MGF 2mg MGF is a splice variant of the IGF gene which increases stem cell count in the muscle and allows for muscle fibers to fuse and mature. This is a process required for growth of adult muscle. Natural MGF is made locally and does not travel into the bloodstream. Synthetic MGF is water based and when administered intramuscularly, travels into the bloodstream. MGF is only stable in the bloodstream for only a few minutes. PEGylation is the act of attaching a Polyethylene glycol (PEG) structure to another larger molecule (in this case, MGF). The PEG acts as a protective coating and the theory here is that this will allow the MGF to be carried through the bloodstream without being broken down.