• Decrease font size
  • Return font size to normal
  • Increase font size
U.S. Department of Health and Human Services

Animal & Veterinary

  • Print
  • Share
  • E-mail


FDA Veterinarian Newsletter 2002 Volume XVI, No V

The following material is taken from a revised CVM Consumer Information Flier prepared in response to numerous inquiries received about the use of hormones in livestock.

The Food and Drug Administration (FDA) is responsible for ensuring that animal drugs and medicated feeds are safe and effective for animals, and that food from treated animals is safe for humans to eat. Certain steroid hormones have been approved for use at very low concentrations to increase the rate of weight gain and/or improve feed efficiency in beef cattle. No steroid hormones are approved for use in poultry. All of the steroid hormonal growth-promoting drugs are available for over-the-counter purchase in the U.S., and are generally administered by the livestock producer at specific stages of production. Residue levels of these hormones in food have been demonstrated to be safe, as they are well below any level that would have a known effect in humans.

Naturally-Occurring Hormones

Estradiol, progesterone, and testosterone are naturally-occurring (endogenous) steroid hormones produced in significant quantities throughout the lifetime of every man, woman, and child, and are required for the proper physiological functioning and maturation of every mammal. All endogenous steroid hormone products marketed in the U.S. for beef growth-promotion are formulated as implantable pellets and are designed to deliver the hormones at a slow, constant rate when injected subcutaneously under the skin of the animal's ear. Numerous scientific studies have demonstrated that, when these drugs are used in accordance with their approved conditions of use, concentrations of the hormones in edible tissues remain within the normal physiological range that has been established for untreated animals of the same age and sex. Because of the slow release of very small amounts of the hormone and a short average half-life (approximately 10 minutes), it has been determined that no preslaughter withdrawal time is necessary to protect the public health. Consumers are not at risk from eating food from animals treated with these compounds because the amount of added hormone is negligible compared to the amount normally found in the edible tissues of untreated animals and that are naturally produced by the consumer's own body.

Synthetic Hormones

Unlike naturally-occurring steroid hormones, there is no natural production of the synthetic compounds, trenbolone acetate, zeranol, and melengestrol acetate (MGA). These compounds are not metabolized as quickly as the naturally-occurring steroid hormones. Therefore, the FDA required, prior to their approval, extensive toxicological testing in animals to determine safe levels in edible tissues for these compounds. 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.

Information about approved hormone products can be found in the Code of Federal Regulations (CFR), Title 21, Parts 522, 556, and 558. Copies of the CFR may be found at your local public or university library and are for sale from the Superintendent of Documents, U.S. Government Printing Office, Washington, DC 20402. In addition, the Code of Federal Regulations may be found on the Internet.