Mechano Growth Factor
When Growth Hormone (GH) was first introduced to the bodybuilding world, everyone had high hopes. Those hopes fizzled out pretty quickly, as bodybuilders experimented with absurdly low dosages (2iu/every other day), necessitated by its high cost. As GH costs fell due to more efficient manufacturing processes (i.e. it was no longer being extracted from cadavers), bodybuilders were able to use more of it, and subsequently began to see better results. We saw the same phenomenon with the anabolic mediator of GH, Insulin-like Growth Factor-1, and later with its analogue, LR3IGF-1.
Now, we’ve seen the emergence of yet another compound further down the hormonal cascade: Mechano Growth Factor (MGH). As you probably know, skeletal muscle responds to resistance training (or any mechanical overload), by increasing its size (hopefully). If you ‘detrain’ that muscle (i.e. don’t use it regularly), it atrophies and gets smaller.
Similarly, when you are in your teens and early twenties GH and IGF-1 levels are high, and as you age, those levels are lowered naturally. And if you’ve been playing along at home, you’re probably figuring out that GH and IGF-1 are pieces of the hormonal puzzle that result in this muscle growth (or loss). These growth factors are produced in the liver and other areas, but also in skeletal tissue in response to training induced damage. Now, pay attention, because this is the important part - growth factors produced within the muscle as a response to resistance training likely play a major role in repair, adaptation, hypertrophy (muscle growth), and also ageing.
Scientists have discovered that many of GH’s anabolic and regenerative effects are actually mediated by insulin like growth factor 1. Thus, the next logical step for bodybuilders (if bodybuilders can be said to follow some kind of logic), was to start experimenting with IGF-1 and later with the more potent version, LR3IGF-1.
The thing is, we now know that IGF-1 actually exists in the body in multiple isoforms. The isoform that seems most useful to us, differs slightly from that which is produced in the liver (IGF-1Ea). It also appears to be the significantly more anabolic of the two we’re looking at here (i.e. that which is produced in the liver vs. that which is produced in the muscle). This is because it is hyper-sensitive to the signals produced by local muscular damage induced by resistance training. This more anabolic isoform of IGF-1 is called “IGF-1Ec” or mechano growth factor (MGF).
That’s right, MGF, the mysterious hormone that seems to be only whispered in e-mails and PMs on the net, is actually just another variant of IGF-1. Yeah, if you’ve used IGF-1 or even GH, then technically, you’ve already been taking advantage of MGF. In fact, if you work out with weights, you’ve been producing your own MGF - as this particular isoform of IGF-1 is only detected in normal muscle after mechanical stimulation (such as resistance training). Remember, MGF is just a name for the particular type of IGF-1 which is produced locally in the muscle as part of the anabolic repair response to resistance training.