I don't think it can be reversed, save surgical reduction. Same goes for the bone growth on the jaw, forehead, etc.
I'm pretty certain that having enlarged internal organs doesn't add to your lifespan.
Also, if your organs are growing like that, any cancerous tendancies do the same thing.
BTW: I doubt any of us here will use GH to the levels that pro-BBers will, nor do it as long as they do. First of all, you could buy a house for the cost of that much GH per year. Secondly, I haven't read a single report on this board of someone complaining about GH gut side effects.