Environmental hormones
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Xenohormones or environmental hormones produced outside of the human body which exhibit
endocrine The endocrine system is a messenger system comprising feedback loops of the hormones released by internal glands of an organism directly into the circulatory system, regulating distant target organs. In vertebrates, the hypothalamus is the neu ...
hormone A hormone (from the Greek participle , "setting in motion") is a class of signaling molecules in multicellular organisms that are sent to distant organs by complex biological processes to regulate physiology and behavior. Hormones are required ...
-like properties. They may be either of natural origin, such as
phytoestrogen A phytoestrogen is a plant-derived xenoestrogen (see estrogen) not generated within the endocrine system, but consumed by eating plants or manufactured foods. Also called a "dietary estrogen", it is a diverse group of naturally occurring nonstero ...
s, which are derived from plants, or of synthetic origin. These compounds are able to activate the same endocrine
receptors Receptor may refer to: *Sensory receptor, in physiology, any structure which, on receiving environmental stimuli, produces an informative nerve impulse *Receptor (biochemistry), in biochemistry, a protein molecule that receives and responds to a n ...
as their natural counterparts and are thus frequently implicated in
endocrine disruption Endocrine disruptors, sometimes also referred to as hormonally active agents, endocrine disrupting chemicals, or endocrine disrupting compounds are chemicals that can interfere with endocrine (or hormonal) systems. These disruptions can cause c ...
. The most commonly occurring xenohormones are
xenoestrogen Xenoestrogens are a type of xenohormone that imitates estrogen. They can be either synthetic or natural chemical compounds. Synthetic xenoestrogens include some widely used industrial compounds, such as PCBs, BPA, and phthalates, which have estro ...
s, which mimic the effects of
estrogen Estrogen or oestrogen is a category of sex hormone responsible for the development and regulation of the female reproductive system and secondary sex characteristics. There are three major endogenous estrogens that have estrogenic hormonal acti ...
. Other xenohormones include xenoandrogens (anabolic-androgenic steroids) and xenoprogesterones. Xenohormones are used for a variety of purposes including contraceptive & hormonal therapies, and agriculture. However, exposure to certain xenohormones early in childhood development can lead to a host of developmental issues including infertility, thyroid complications, and early onset of puberty. Exposure to others later in life has been linked to increased risks of testicular, prostate, ovarian, and uterine cancers.


Etymology

The term is derived from the
Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...
words ξένος (''xenos''), meaning "stranger". The prefix "xeno-" is added because xenohormones are foreign to the body, even though they mimic natural hormones.


Uses

Xenohormones are found in a variety of different consumer products, agricultural products, and chemicals. Common sources of Xenohormones include: * Contraceptives and Hormone Therapies Xenohormones and xenoestrogens are commonly used in oral contraceptives such as birth control pills and hormone replacement therapies due to their similarities to natural hormones. * Agriculture Synthetic estrogenic drugs such as the bovine growth hormone (BVG) are commonly used to increase the size of cattle and maximize the amount of meat and dairy product that can come from them. Xenohormones are also found in certain pesticides, herbicides, and fungicides. * Plastics Xenohormones are found in almost all plastics, and they appear in many consumer products that use plastic elements or plastic packaging. Common xenohormones in plastics and other industrial compounds include BPA,
Phthalate Phthalates (, ), or phthalate esters, are esters of phthalic acid. They are mainly used as plasticizers, i.e., substances added to plastics to increase their flexibility, transparency, durability, and longevity. They are used primarily to soften ...
s, PVC, and
PCBs Polychlorinated biphenyls (PCBs) are highly carcinogenic chemical compounds, formerly used in industrial and consumer products, whose production was banned in the United States by the Toxic Substances Control Act in 1979 and internationally by t ...
. These can be found in several household items, including plastic dishes and utensils, Styrofoam, cling wrap, flooring, toys, and other items containing plastic or plasticizers. In 2000, the FDA banned the use of phthalates in baby toys due to health concerns. * Cleaning and Cosmetic Products Many household products can contain certain xenohormones, including laundry detergent, fabric softeners, soap, shampoo, toothpaste, makeup and cosmetic products, feminine hygiene products.


Endocrinology

Xenohormones can come from a variety of sources, both natural and man-made. Man-made xenoestrogens are often found in cosmetic products, some foods, certain pharmaceuticals, plastic products, flame retardants, and pesticides. Naturally occurring xenoestrogens include phytoestrogens (estrogen-like compounds from plants) and mycoestrogens (estrogen-like compounds from fungi). While natural xenohormones exist, there are not as many compounds found in nature which are capable of interacting with human
androgen receptor The androgen receptor (AR), also known as NR3C4 (nuclear receptor subfamily 3, group C, member 4), is a type of nuclear receptor that is activated by binding any of the androgenic hormones, including testosterone and dihydrotestosterone in th ...
s, so humans are most likely to come into contact with man-made xenoandrogens by taking anabolic steroids or through pollutants which contain xenoandrogens. "Organochlorine pesticides,
polychlorinated biphenyl Polychlorinated biphenyls (PCBs) are highly carcinogenic chemical compounds, formerly used in industrial and consumer products, whose production was banned in the United States by the Toxic Substances Control Act in 1979 and internationally by t ...
s (PCBs), and polychlorinated dibenzo-''p''-dioxins/dibenzofurans (PCDDs/PCDFs)" are several pesticides known to contain xenoandrogens. When present in excessive amounts within the human body, xenohormones can cause a host of health issues due to their disruption of the endocrine system. The name given to these exogenous (coming from an external source) hormones is “
endocrine disruptor Endocrine disruptors, sometimes also referred to as hormonally active agents, endocrine disrupting chemicals, or endocrine disrupting compounds are chemicals that can interfere with endocrine (or hormonal) systems. These disruptions can cause c ...
s,” due to their tendency to mimic the behaviors of naturally produced bodily hormones. The negative effects of excessive xenoestrogen involve a long list of developmental abnormalities, especially when the exposure occurs during a critical postnatal period. When high levels of xenoestrogen are experienced shortly after birth, “urogenital tract and nervous system development” are hindered, as they are known to be “especially sensitive to hormonal disruption.” When exposure occurs during this early stage of life, these effects tend to be permanent. The consequences of excessive xenohormone exposure in adulthood are different, and typically more temporary in nature. This is to say that the health risks can be minimized if the individual is removed from their state of excessive exposure. Xenohormone-related issues in adults frequently take the form of increased cancer risk in reproductive/secondary sexual areas (“breast, uterine, ovarian, prostate, testicular.” Sperm count in men and fertility in women have also been attributed to xenohormone exposure in adulthood. When present in the body, xenohormones can bind with estrogen receptors in the brain, leading to a disruption in the endocrine system as a whole. Such hormones have also been observed to interfere with the production of proteins. These “endocrine disruptors” have also been found to affect the levels and behaviors of a number of other bodily hormones. Because of this, it is difficult to establish a definitive relationship between xenohormones and health problems, making effects hard to predict.


Effect on Humans

Research indicates that exposure to certain xenohormones can result in severe health risks, including infertility, early puberty, thyroid problems, endometriosis, and certain types of cancers. It has also been claimed that certain xenoestrogens, most commonly phytoestrogens and mycoestrogens can have beneficial health effects, though it is not yet clear to what extent the benefits are present or whether they outweigh the possible health risks of these compounds. Xenohormones and other endocrine disrupting compounds (EDCs) can block and disrupt the natural function of hormones and the endocrine system of the body, so conditions related to hormone imbalance or an improperly functioning endocrine system are possible after exposure. Certain xenohormones have been detected in the breast tissue of humans with breast cancer, which hints at a correlation between xenoestrogen exposure and breast cancer. This can occur in both men and women, although women may be more likely to develop breast cancer from xenohormones due to the popularity of cosmetic products among women. It may also be the case that women simply develop breast cancer in general more often than men, as there is no conclusive evidence that xenoestrogen-related breast cancers are more common among women than men after adjusting for the differing rates of breast cancer. Xenohormones are also linked to increased risks of testicular, prostate, ovarian, and uterine cancers.


Environmental Risks

The use of xenohormones in both agriculture and industry raises concerns about their effect on the environment and public health. Xenohormones have been observed to contaminate food and water through the use of pesticides, hormone treatments in livestock, and plastic packing such as water bottles. In addition to posing health threats for humans, EDCs and xenohormones also pose health risks to wildlife. For example, PCBs can interrupt animal fetal development, cause changes in an animal's response to stress, and cause thyroid and immune function diseases. Plastics specifically pose a commendable environment threat due to the fact that many of them do not decompose. Xenohormones in plastic litter have the potential to contaminate natural water sources and expose both humans and wildlife to a variety of different EDCs. Because Xenohormones such as BPA have demonstrated health concerns for humans and animals, both the Environmental Protection Agency (EPA) and FDA have conducted research and issued statements and regulations to reduce their impact on public health and the environment. In March 2010, the EPA published its Bisphenol A (BPA) Action Plan, which details measures to reduce the impact of BPA on aquatic species. These measures include identifying BPA as “a substance that may present an unreasonable risk of injury to the environment” and introducing new regulations to minimize the environmental impact of xenohormones like BPA.


See also

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Xenobiotic A xenobiotic is a chemical substance found within an organism that is not naturally produced or expected to be present within the organism. It can also cover substances that are present in much higher concentrations than are usual. Natural compo ...
*
Xenoestrogen Xenoestrogens are a type of xenohormone that imitates estrogen. They can be either synthetic or natural chemical compounds. Synthetic xenoestrogens include some widely used industrial compounds, such as PCBs, BPA, and phthalates, which have estro ...
*
Anabolic steroid Anabolic steroids, also known more properly as anabolic–androgenic steroids (AAS), are steroidal androgens that include natural androgens like testosterone (medication), testosterone as well as synthetic androgens that are structurally related ...
*
Bisphenol A Bisphenol A (BPA) is a chemical compound primarily used in the manufacturing of various plastics. It is a colourless solid which is soluble in most common organic solvents, but has very poor solubility in water. BPA is produced on an industrial s ...
*


References

{{Reflist Endocrinology Environmental science Hormones Toxicology