Editing Hyperthyroidism (section)

===Dogs===
Hyperthyroidism is much less common in [[dog]]s compared to cats.<ref>{{cite book| vauthors = Ford RB, Mazzaferro E |title=Kirk & Bistner's Handbook of Veterinary Procedures and Emergency Treatment|date=2011|publisher=Elsevier Health Sciences|location=London|isbn=978-1-4377-0799-1|page=346|edition=9th}}</ref> Hyperthyroidism may be caused by a thyroid tumor. This may be a thyroid [[carcinoma]]. About 90% of carcinomas are very aggressive; they invade the surrounding tissues and [[Metastasis|metastasize]] (spread) to other tissues, particularly the lungs. This has a poor [[prognosis]]. Surgery to remove the tumor is often very difficult due to [[metastasis]] into [[arteries]], the [[esophagus]], or the [[windpipe]]. It may be possible to reduce the size of the tumor, thus relieving symptoms and allowing time for other treatments to work.{{Citation needed|date=April 2010}} About 10% of thyroid tumors are benign; these often cause few symptoms.{{Citation needed|date=April 2010}}

In dogs treated for [[hypothyroidism]] (lack of thyroid hormone), iatrogenic hyperthyroidism may occur as a result of an overdose of the thyroid hormone replacement medication, [[levothyroxine]]; in this case, treatment involves reducing the dose of levothyroxine.<ref name=HypoT>{{cite web|url=http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/40602.htm|title=Hypothyroidism|publisher=Merck Veterinary Manual|access-date=27 July 2011|url-status=live|archive-url=https://web.archive.org/web/20110526152610/http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm%2Fbc%2F40602.htm|archive-date=26 May 2011}}</ref><ref>{{cite web|url=http://usa.leventa.com/Vet/label.asp|title=Leventa-Precautions/Adverse Reactions|publisher=Intervet|access-date=27 July 2011|url-status=live|archive-url=https://web.archive.org/web/20120114181242/http://usa.leventa.com/Vet/label.asp|archive-date=14 January 2012}}</ref> Dogs which display [[coprophagy]], the consumption of feces, and also live in a household with a dog receiving levothyroxine treatment, may develop hyperthyroidism if they frequently eat the feces from the dog receiving levothyroxine treatment.<ref name="Shadwick 2013">{{cite journal | vauthors = Shadwick SR, Ridgway MD, Kubier A | title = Thyrotoxicosis in a dog induced by the consumption of feces from a levothyroxine-supplemented housemate | journal = The Canadian Veterinary Journal | volume = 54 | issue = 10 | pages = 987–989 | date = October 2013 | pmid = 24155422 | pmc = 3781434 }}</ref>

Hyperthyroidism may occur if a dog eats an excessive amount of thyroid gland tissue. This has occurred in dogs fed commercial dog food.<ref name="Broome 2015">{{cite journal | vauthors = Broome MR, Peterson ME, Kemppainen RJ, Parker VJ, Richter KP | title = Exogenous thyrotoxicosis in dogs attributable to consumption of all-meat commercial dog food or treats containing excessive thyroid hormone: 14 cases (2008-2013) | journal = Journal of the American Veterinary Medical Association | volume = 246 | issue = 1 | pages = 105–111 | date = January 2015 | pmid = 25517332 | doi = 10.2460/javma.246.1.105 | doi-access = free }}</ref>