Currently, six different steroidal hormones are approved by the FDA for use in “food animals.” These are the natural hormones estradiol, progesterone, testosterone, and the synthetic hormones trenbolone acetate, progestin melengestrol acetate, and zeranol, all of which make animals grow faster and/or produce leaner meat for food. Dairy cattle are often treated with recombinant bovine growth hormone (rBGH) to increase milk production. Hormones are banned for use in poultry in the . (but that doesn’t stop chicken producers from marketing their birds as hormone-free!).
Some of the approved drugs are synthetic versions of the natural hormones, such as trenbolone acetate and zeranol. Just like the natural hormone implants, before FDA approved these drugs, FDA required information and/or toxicological testing in laboratory animals to determine safe levels in the animal products that we eat (edible tissues). Furthermore, FDA required that the manufacturers demonstrate that the amount of hormone left in each edible tissue after treatment is below the appropriate safe level. As described above, a safe level is a level which would be expected to have no harmful effect in humans.