Until 1980, the use of growth hormones in farm animals, both endogenous (produced within) and exogenous (originating externally - injected /in feed etc), was completely prohibited in Denmark, Greece, Germany, Italy and the Netherlands. The five other EU member countries, including the second and third largest beef producers, France and the United Kingdom, permitted their use. (The use of growth hormones was particularly common in the U.K., where beef production was heavily industrialized.) in 1980, and the commissioning of a major scientific study was carried out into the use of estradiol, testosterone, progesterone, trenbolone, and zeranol in 1981.
Japanese researchers revealed in a recent study that "The high estrogen concentrations in Japanese chicken, USA chicken, and USA beef have been attributed to the residue of external estrogen in the feed given to the livestock. The nearly zero level found in Japanese beef and Brazilian chicken is considered to be natural endogenous amount without estrogen supplementation. The estrogen levels in meat are much lower than those of contraceptive pills (0.035 mg/tab). Even so, when considering lifetime exposure to meat containing higher level of estrogen than human fat tissue, estrogen intake from daily meat consumption cannot be disregarded as a factor governing human health. Consequently, dietary estrogen intake from meat might promote estrogen accumulation in the human body and could be related to the incidence of hormone-dependent cancers"
The labeling of estrogen-only products in the U.S. now includes a warning that unopposed estrogen, without progesragen, therapy increases the risk of endometrial cancer and breast cancers. These warnings are based on reviews of data, and on January 8, 2003 the United States Food and Drug Administration changed the labeling of all estrogen and estrogen with progestin products for use by postmenopausal women to include a new boxed warning about cardiovascular and other risks.