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Estrogens


Natural steroid hormones as well as synthetic sex steroids are very potent endocrine-disrupting compounds.

Gonadal Steroids


Estrogens, androgens, and progestins are produced in male and female organisms as well, but in different amounts. Steroid hormones are lipophilic, fat-soluble molecules, which are mainly excreted as water-soluble glucoronates or sulphate conjugates. Under environmental conditions these conjugates are quickly hydrolyzed, leading to the free hormones or their metabolites.

Different organisms excrete various amounts of sex steroids, depending on parameters such as age, state of health, diet, or pregnancy. The amount of excreted estrogens of pregnant women can be 1000 times higher, depending on the progress of the pregnancy.

A very important source of natural estrogens is livestock in agriculture. Here, hundreds of animals are often living at one site, meaning that sewage and manure probably contain high concentrations of sex steroids. The routes of natural estrogens into the environment are different, depending on the respective source (Lintelmann et. al. 2003).

Phytoestrogens


Many plants produce chemicals that mimic or interact with hormone signals in animals. The estrogen-like phytoestrogens are the most studied of all the phytochemicals. In general, phytoestrogens are weaker than the natural estrogen hormones (such as estradiol) found in humans and animals or the very potent synthetic estrogens used in birth control pills and other drugs (Jefferson et al. 2002a).

Exposure to phytoestrogens is mainly through diet. The estrogenic plant compounds are widespread in food, including herbs and seasonings (garlic, parsley), grains (soybeans, wheat, rice), vegetables (beans, carrots, potatoes), fruits (date, pomegranates, cherries, apples), and drinks (coffee). The two most studied phytoestrogen groups are lignans and isoflavones. Lignans are products of intestinal microbial breakdown of compounds found in whole grains, fibers, flax seeds and many fruits and vegetables. Enterodiol and enterolactone are examples of lignans. Isoflavones, such as genistein and daidzein, occur in soybeans and other legumes.

There are currently differing opinions about the role of phytoestrogens in health. For adults, when consumed as part of an ordinary diet, phytoestrogens are considered safe and possibly beneficial. Some studies on cancer incidences in different countries suggest that phytoestrogens may help protect against certain cancers (breast, uterus, and prostate). However, it is still unclear whether this beneficial effect is due to increased amounts of phytoestrogens in the diet or to the resulting low fat content of the diet. Similar beneficial effects of dietary phytoestrogen supplements have not been documented. On the contrary, eating very high levels of phytoestrogens may pose health risks. Studies with laboratory and farm animals, as well as wildlife eating high amounts of phytoestrogen-rich plants, have documented reproductive problems (e-hormone).

Synthetic Steroids: Pharmaceuticals


This group of pharmaceuticals mainly consists of oral contraceptive (shttp://toxipedia.org/display/toxipedia/Hormonal+Contraception) (ovulation-inhibiting hormones) as well as steroids used for substitution therapy during menopause. Natural hormones like estradiol or progesterone are not suitable for oral applications-or only at higher dosage-because they are quickly metabolized (i.e., deactivated) and excreted. Therefore, mainly synthetic steroids are used for oral application (Lintelmann et. al. 2003).

Ethylination or alkylation of the natural compound prevents metabolization and guarantees the desired effect. The most common estrogen-like synthetic steroids are ethinylestradiol and mestranol, whereas the progestagenic component in oral contraceptives can be norgestrel or norethisterone. A further important group of pharmaceutical hormones are steroids used in agriculture during cattle farming (Lintelmann et. al. 2003).

References


Lintelmann J., Katayama A., Kurihara N., Shore L., Wenzel A. 2003. Endocrine disruptiors in the environment. IUPAC Technical Report. Pure and Applied Chemistry, 75: 631-681.

Jefferson WN, Padilla-Banks E, Clark G, and Newbold RR. 2002a. Assessing estrogenic activity of phytochemicals using transcriptional activation and immature mouse uterotrophic responses. Journal of Chromatography. B Analytical Technologies in the Biomedical and Life Sciences 777(1-2):179-189.


e hormone Website. Center for Bioenvironmental Research (Tulane and Xavier Universities). Endocrine Disrupting Chemicals-Phytoestrogens. Accessed 2/24/2011.

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