According to the European Union’s Scientific Committee on Veterinary Measures Relating to Public Health, the use of six natural and artificial growth hormones in beef production poses a potential risk to human health.iii These six hormones include three which are naturally occurring—Oestradiol, Progesterone and Testosterone—and three which are synthetic—Zeranol, Trenbolone, and Melengestrol.
The Committee also questioned whether hormone residues in the meat of "growth enhanced" animals and can disrupt human hormone balance, causing developmental problems, interfering with the reproductive system, and even leading to the development of breast, prostate or colon cancer.iv
Children, pregnant women and the unborn are thought to be most susceptible to these negative health effects. Hormone residues in beef have been implicated in the early onset of puberty in girls, which could put them at greater risk of developing breast and other forms of cancer. The European Union’s Committee reported that as of 1999, no comprehensive studies had been conducted to determine whether hormone residues in meat can be cancer-causing.v