Found naturally in animals' bodies, hormones are chemicals that control processes like growth and metabolism. Synthetic (man-made) hormones have been developed for a number of purposes, including treatment of hormonal disorders in people, and promotion of accelerated growth in farm animals. One of the most well-known and controversial hormones used in farming is recombinant Bovine Growth Hormone, or rBGH, which is genetically engineered and injected into dairy cattle. Scientists have linked excess hormones to cancer. See our "rBGH" page for more information.