There is a very good article on another website about using IGF's. They made a strong case that the only time to inject is immediately after exercise. Made the argument that it will go and be absorbed where the muscles have been worked. If you take it at other times it goes to the organs most full of blood which are your intestines, so you get gut growth.
They also made the point that it is effective in very small doses. Like 20 micro grams after working out, versus other things you may have read like up to 80 to 100 per day.