Chemicals found naturally in animals' bodies 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 also for promotion of unnaturally fast 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. rBGH is not permitted for use in Canada. Scientists have linked excess hormones to cancer.