Your body reacts to IGF-1 the same way it dose to HGH, where your body starts to produce a hormone called Somatostatin. Somatostatin is a natural hormone that your body uses to shut down GH and IGF-1 receptors to prevent a disturbance in homeostasis. Somatostatin can be involved in GH production down regulation. So the longer that you are on GH the more Somatostatin that your body will produce. So if you look at it this way, GH is just a precursor to IGF-1, so because of how much more potent IGF-1 is, it will cause a greater disturbance in your body's homeostasis, so therefore you body will release massive amounts of Somatostatin, rendering the IGF-1 ineffective after only 4 weeks or so. Keeping this in mind, it should be pretty obvious that you will get the most out of GH using shorter cycles of it. Here is something to think about, when children experience growth spurts, their pituitary gland secretes about 2 iu's of GH up to 7 times a day. But they only do this for a brief period of 4-5 days, over/up to a 3 week period. So even GH would be more effective if you limited it's use to around 4 weeks on 4 weeks off. Hope this was helpful.
