Bovine somatotropin (bST) is a naturally occurring protein hormone produced by a cow’s pituitary gland. Present in all cows, bST regulates metabolic activities, helping young cattle grow and adult cows produce milk. It is not a steroid but rather a protein hormone. A small amount of this hormone is naturally present in all milk, including organic products. In fact, hormones are naturally present in all foods of plant and animal origin, including milk. When milk is consumed, the small amount of bST present is broken down completely by the body’s digestive system, just as is any other protein.