yes, every excercise increases production of growth hormone, but squats and heavy leg excercises increase it a hell of a lot more. thats what this guy told me that works at the gym i go to. he said they did an experiment at some college, where they had a group of guys only do upper body workouts for a certain amount of time, and another group do upper body workouts and leg workouts, and the second group experienced more muscle growth, upper and lower body, then the first group. he told me it was a big difference too.
it makes sense...given you can squat like 2 or 3 times what you can bench. heavier weights = more growth hormone needed to grow. same for compound excercises, more muscles being worked = more growth hormones.
not sure what natural test is though, i thought test just raises protien synthesis.