Environmental Hormones Endocrine Disruptors

Deception Hormonal Chaos and The Feminization of Nature— Our Future at Risk chronicle the perceived, predicted, and observed problems associated with endocrine disruptors.50 Skepticism regarding the human impact of environmental contaminants has been discussed in several books including The Skeptical Environmentalist and Naturally Dangerous Surprising Facts About Food, Health and the Environment,51 and John Stossel (ABC television) remains a consistent skeptic with his features on junk science. 

For humans, except for cases where high levels of exposure have occurred (for example, in the therapeutic use of diethylstilboestrol), the data is inconsistent and inconclusive. Information on levels of exposure is lacking and there is no firm evidence for a Hnk between low level exposure and adverse health outcomes in the human population. For all the adverse health outcomes the evidence of association with environmental exposure to endocrine disruptors is weak (except in the case of minor effects on thyroid hormones, where evidence is moderate). In some cases, such as changes in sperm count, a possible connection is scientifically plausible. Further evidence is needed, and especially evidence that Hnks actual exposure levels in humans to effects. ... 

The term endocrine disruptors was first used by Theo Colborn and Peter Thomas in 1992. In 1996, the US Environmental Protection Agency (EPA) convened a panel called the Endocrine Disruptors Screening and Testing Advisory Committee to make recommendations to EPA concerning endocrine disruptors. The term endocrine disruptors has been used interchangeably with hormonally active agents and endocrine modulators. As the term is used now, endocrine disruptors include any substance that affects the synthesis, secretion, transport, binding, action, inactivation, or elimination of natural hormones in the body. 

Xenoestrogens, exhibiting a wide molecular diversity, are found in a number of cosmetic products, such as plasticizers, perfume fixatives, and solvents (e.g., dibutyl phthalate), industrial chemicals and pollutants such as insecticides (e.g., methoxychlor, DDT, and DDE), epoxy resins, and polycarbonate (e.g., bisphenol A), and herbicides (e.g., simazine). This group of chemicals has been classified as environmental endocrine disruptor compounds (EDCs), defined as exogenous agents that interfere with the synthesis, transport, binding, action, or elimination of natural hormones in the body that are responsible for the maintenance of homeostasis, reproduction, development, and/or behavior. A list of representative chemicals is shown in Table 1 based on commercial usage. 

Endocrine disruption is a newly discovered mode of action and has encouraged a great deal of research. Compared to some of the other mechanisms described in this chapter, endocrine disruption is more subtle with alterations in reproductive physiology and morphology often being the effects, instead of death. Because of the hormone-like activity, these compounds can have identifiable effects at very low concentrations. It is not yet clear what the overall importance of endocrine disruptors are in creating environmental impacts compared to other modes of action. 

Recently, the hazardous effects of endocrine disruptors (environmental hormones) such as bisphenol A and nonylphenol on the human body have been reported, and led to the initiation of many studies concerning the detection and structural determination of these compounds present in tiny amounts [57]. As one of the QSAR analyses of environmental hormones, the relationship between their biological activity and chemical hardness has been reported [16]. By applying these analytical methods, the molecular toxicity and estrogen-like activity of environmental hormones have been found... 

A different form of toxicity occurs in the estrogen and androgen receptors when environmental chemicals have the ability to bind to them. Acting both as agonists or antagonists, these so-called endocrine disruptors are responsible for a number of hormone-related cancers, in addition to their roles in adversely affecting sexual development and reproductive fertility. 

According to Susan Brien et al. (2000, the single hit obtained by combining DDT and impotence), 33 million American men have erection problems, which may be caused by environmental contaminants. This problem inspired her and her co-workers to see if p,p-DDE disturbed erection in rats. They found that high doses (500 mg/kg) of DDE indeed had such an effect and concluded "The endocrine disruptor p,p-DDE can markedly interfere with erectile function and demonstrates persistence after a single dose. This supports our novel concept that environmental hormones may cause erectile dysfunction."... 

Can we expect environmental endocrine disruptors to affect the sexual development of the human fetus In my opinion, the answer is an absolute yes, if only because we know that endocrine disruptors act like foreign hormones and thereby disrupt natural hormone physiology. Hormones are critical in fetal sexual and brain development. Exposure of the fetus to hormones can produce profound changes in development. In the case of androgenic hormones, for example, exposure diverts a genetic female to take on the phenotypic appearance of a male, and these hormones change the areas of the brain that ordinarily differ between the sexes (sexually dimorphic areas). 

Environmental estrogens are part of a group of chemicals known as endocrine disruptors that can affect hormone action in an animal or person. This group of chemicals first gained attention in the 1980s when several environmental studies indicated that sex ratios of some reptiles and amphibians in specific areas were abnormal. Entire populations were composed primarily of females, and the males... 

Dysfunction of the endocrine system could be due to either hyperfunction (excessive hormone production or responses) or hypofunction (insufficient hormone production or responses). Environmental chemicals that have the potential to perturb the endocrine system are known as endocrine or, synonymously, hormone disruptors. 

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