Commercial milk is loaded with growth hormones. That's why we have 200 lb third graders.
Yep it's the hormones, not the sedentary Nintendo- and internet-laden lifestyles, oversized dietary portions, and parents feeding them soft drinks and Twinkies to shut them up that does it.
BHG (bovine growth hormones) and HGH (human growth hormones) have different protein structures so cross-species sensitivity is virtually nil. Just as bovine semen will not fertilize a human egg, neither will BGH effectively fill the roll of HGH in the human body. Plus, BGH is a protein and proteins are broken down in the digestive tract anyway. Even if there were large amounts of BGH present in beef there is little chance of it ever making it past your gut, and what might reach the bloodstream is not compatible with human physiology.
Brad