Actually Gh in its self is quite a useless substance, the synergistic effect of Gh and insulin create the substance known as Igf 1 , it is this hormone that is responsable for ongoing cellular growth with in the body. Gh has only has a half life of around 1 hr with in the system, and it is with in this time the conversion to Igf1 should take place,Igf1 then has a half life with in the body of up to 3 days in which time it promotes the new and re growth of celluable tissue.
The added enhanced environment of Positive nitrogen retention caused by the intake of Anabolics enhance and add the celluable growth effect whilst the introduction of a elevated testosterone count aids the cells new and old ability to achieve Maxim muscle hypertrophy.
All this activity in turn increases the body's metabolic rates thus increasing the thermogenic status of the individual which in turn aids the body in using its fat stores as a energy source !!!
Problem is Igf1 is not stressed(trained)muscle specific and causes celluable growth at all levels, one of the problems that can occur is that fibrous tissue can be strained and damaged through the rapid increases in strength caused by the the larger and new plentiful muscle growth.
Those who have used Gh and found little or no result either got sold bogus Gh or did not have there insulin equation right, also the environment they were creating in their body's might have not been anabolic and nutrient dense enough to support the increased cellular growth.
Gh is useless really but the synergistic effect of all the above is the best growth combination one can get !!!