My legs respond really well to training and i obviously have a gift in that area in the past 5 months ive taken my leg size from 21" to 25.5"

But my upper body seems to be very sluggish in growing and leaves me a bit out of proportion, if i can build well in my legs surely i am producing lots of the right hormones etc... but why does my upper body remain like this, is it due to messages sent to the muscles or is my training wrong?