HORMONES AS MEAT GROWTH ENHANCERS. “Since the 1950s, the Food and Drug Administration (FDA) has approved a number of steroid hormone drugs for use in beef cattle and sheep, including natural … and their synthetic versions. These drugs increase the animals’ growth rate, the efficiency … and the leanness of their meat.”
http://www.fda.gov/AnimalVeterinary/SafetyHealth/ProductSafetyInformation/ucm055436.htm