Editing Endocrine disruptor (section)

==U-shaped dose-response curve==
{{See also|Hormesis}}
Most toxicants, including endocrine disruptors, have been claimed to follow a U-shaped [[dose-response relationship|dose-response curve]].<ref>{{cite journal | vauthors = Calabrese EJ, Baldwin LA | title = Toxicology rethinks its central belief | journal = Nature | volume = 421 | issue = 6924 | pages = 691–2 | date = February 2003 | pmid = 12610596 | doi = 10.1038/421691a | bibcode = 2003Natur.421..691C | s2cid = 4419048 }}</ref> This means that very low and very high levels have more effects than mid-level exposure to a toxicant.<ref>{{cite report | vauthors = Steeger T, Tietge J | url = http://www.epa.gov/scipoly/sap/2003/june/finaljune2002telconfreport.pdf | archive-url = https://web.archive.org/web/20040711101409/http://www.epa.gov/scipoly/sap/2003/june/finaljune2002telconfreport.pdf | archive-date = 11 July 2004 | title = White Paper on Potential Developmental Effects of Atrazine on Amphibians | number = 54 | date = 29 May 2003 }}</ref>

Endocrine-disrupting effects have been noted in animals exposed to environmentally relevant levels of some chemicals. For example, a common [[flame retardant]], [[PBDE|BDE]]-47, affects the reproductive system and thyroid gland of female rats in doses similar to which humans are exposed.<ref name="pmid18335096">{{cite journal |vauthors=Talsness CE, Kuriyama SN, Sterner-Kock A, Schnitker P, Grande SW, Shakibaei M, Andrade A, Grote K, Chahoud I | title = In utero and lactational exposures to low doses of polybrominated diphenyl ether-47 alter the reproductive system and thyroid gland of female rat offspring | journal = Environmental Health Perspectives| volume = 116 | issue = 3 | pages = 308–14 |date=March 2008 | pmid = 18335096 | pmc = 2265047 | doi = 10.1289/ehp.10536 | bibcode = 2008EnvHP.116..308T }}</ref>

Low concentrations of endocrine disruptors can also have synergistic effects in amphibians, but it is not clear that this is an effect mediated through the endocrine system.<ref name="pmid16818245">{{cite journal |vauthors=Hayes TB, Case P, Chui S, Chung D, Haeffele C, Haston K, Lee M, Mai VP, Marjuoa Y, Parker J, Tsui M | title = Pesticide mixtures, endocrine disruption, and amphibian declines: are we underestimating the impact? | journal = Environmental Health Perspectives| issue = S–1| pages = 40–50 |date=April 2006 | volume = 114  | pmid = 16818245 | pmc = 1874187 | doi = 10.1289/ehp.8051 | bibcode = 2006EnvHP.114S..40H }}</ref>

A consensus statement by the Learning and Developmental Disabilities Initiative argued that "The very low-dose effects of endocrine disruptors cannot be predicted from high-dose studies, which contradicts the standard 'dose makes the poison' rule of toxicology. Nontraditional dose-response curves are referred to as non-monotonic dose response curves."<ref name='urlwww.iceh.org'/>

It has been claimed that [[tamoxifen]] and some [[phthalates]] have fundamentally different (and harmful) effects on the body at low doses than at high doses.<ref>{{cite web | vauthors = Curwood S, Young J | url = http://www.loe.org/shows/segments.htm?programID=09-P13-00036&segmentID=3 | title = Low Dose Makes the Poison | work =  Living on Earth | date = 4 September 2009 }}</ref>