GH is not catabolic at all
it has a metabolism increasing effect, meaning it increases protein turnover (both accretion and degradation), but theres an increase in net protein synthesis so its more anabolic than catabolic
btw, AAS do the same thing. very few people know this but testosterone actually increases protein degradation, meaning muscle loss. it just increases protein synthesis by a much greater degree, so that in the end you gain muscle. tren does the opposite. it actually DECREASES protein synthesis but DECREASES protein degradation to a much stronger degree either, so in the end its = gains. another reason for test+tren being such a great stack.
the whole thing with tren is debatable though, ive seen studies on tren showing no increase in protein degradation and an increase in protein synthesis too. its probably dependant on a lot of factors.
as always, 100 studies, 100 opinions.
but ive never seen a single study showing GH to be catabolic to muscle tissue