Because of the high demand on producers of meat and Chicken to get food out to the masses as quick as possible, the injection of hormones (among others) has become common practice.
Unbeknown to the end user this has an effect on your body as the notion of you are what you eat is becoming more and more popular.
Below is an article that has some interesting points on this subject.
http://www.livestrong.com/article/98816-effects-growth-hormones/
Natural Meat’s Chicken and Meat is Hormone FREE