A concern about hormones in meat, especially synthetic hormones, is a good reason to buy meat from organically raised animals.
Almost all conventional (not organically raised) livestock in the U.S. are treated with hormones.
Hormones are given to an estimated 90% of U.S. beef cattle, 100% of U.S. pigs, and were found to have been illegally used in 90% of veal calves. There are six approved hormones for beef cattle, four of which are synthetic (one of which is used in feed).
Steroid hormones are implanted into livestock for growth: to create increased weight gain and increased muscle mass (meat).
The hormones are supposed to be implanted into the animals' ears. But illegal use is apparently common, even typical; one study showed that half of tested slaughtered animals had hormones illegally implanted directly into the muscle. The muscle is the meat that someone will eat.
The USDA does not test for hormone residue. When the European Union tested U.S. beef, it found that 12% contained hormone residue, including one hormone illegal in the U.S. The European Union does not allow the use of hormones.
Hormone residue in meat promotes hormone-sensitive cancer and affects the sexual development of children. Runoff from farm waste also contains these hormones and pollutes drinking water and the environment.
Animals raised organically are never treated with hormones.
Organic Consumers Association: Fact Sheet on Hazards of Hormone Implants or Injections in Beef
The London Daily Mail: The Inside Scoop on American Feedlot Beef