|Classification and external resources|
This can be due to:
- One testicle not descending into the scrotum during normal embryonic or fetal development (3–4% of 'normal' live births), also known as undescended testis or cryptorchidism. In this case the testis is within the abdominal cavity, somewhere along the normal route of descent – most commonly, within the inguinal canal. Such a testis has an increased risk of malignancy.
- One testicle may disappear during development (the so-called vanishing testis) due to some intrauterine insult. This is thought to be most likely vascular, such as testicular torsion.
- One testicle may have been surgically removed through orchiectomy.
- One testicle may be injured.
Due to testicular cancer
- Lance Armstrong, American bicyclist.
- Frank Church, late U.S. Senator and a presidential aspirant in 1976. His monorchism was revealed publicly during the 1976 presidential campaign.
- Tom Green, Canadian comedian-actor.
- Mark Latham, former Australian politician.
- Geoff Horsfield, English footballer.
- Nenê, Brazilian basketball player.
- Kevin Curtis, American football player.
- Nigel Farage, leader of the UK Independence Party.
- Bobby Moore, English footballer and World Cup winner.
Michael Kosior. 2016 he lost a testicle while masturbating
Due to injury
- Archibald Douglas, 4th Earl of Douglas, magnate of the Kingdom of Scotland, and Peer of France. Lost in 1403, while fighting at the Battle of Shrewsbury (He had previous year, lost an eye at the Battle of Homildon Hill).
- Francisco Franco, dictator of Spain.
- Troy Bayliss, world superbike champion in 2001, 2006 and 2008. In 2007 he lost a testicle during a race at Donington Park.
- Brian Foster, American mixed martial artist.
Due to cryptorchidism
- Adolf Hitler, German dictator (alleged).
- Bruce Lee, American-Chinese actor and martial arts instructor.
- Mao Zedong, known as Chairman Mao, Chinese revolutionary.
Monorchism in nonhuman animals
Although extremely rare, monorchism has been observed to be characteristic of some animal species, notably in beetles.
An individual having monorchism can be referred to as monorchid.
- http://www.salon.com/health/feature/1999/07/29/lance/index.html Salon.com - Lance Armstrong
- "1984-01-23 HOSPITALIZED. Frank Church, 59". TIME. 1984-01-23. Retrieved 2010-05-13.
- http://www.usrf.org/tomgreen.shtml Urological Sciences Research Foundation page on Tom Green
- http://www.abc.net.au/gnt/health/Transcripts/s951129.htm ABC: Testicular Cancer and Mark Latham
- Baggaley, Michael (July 22, 2009). "Port Vale: Horsfield hoping his luck can rub off on Valiants". The Sentinel. Retrieved 2009-07-22.
- "Nuggets: Nene's testicular tumor malignant, cancer isolated". USA Today. January 22, 2008. Retrieved 2012-02-19.
- "After surgery for cancer, wide receiver Kevin Curtis gets a chance with Miami Dolphins". Palm Beach Post. December 17, 2010. Retrieved 2012-02-19.
- Farage, Nigel (13 March 2015). "Nigel Farage: Cancer, a lemon-sized testicle and how the NHS failed me". The Daily Telegraph. Retrieved 10 April 2015.
- "David Beckham is great, but Bobby Moore was one of a kind". Mirror. February 14, 2009. Retrieved 2012-02-21.
- Chronicle of John Hardyng, ed. Ellis, H., p.381. London, 1812. 
- "BBC News - Spain's Franco 'had one testicle'". Retrieved 7 December 2015.
- "Hard Man Bayliss". Visordown. Retrieved 7 December 2015.
- "MMA cost Brian Foster a nut". Rebellion Media. April 13, 2011. Retrieved 2012-02-19.
- "Hitler really did have only one testicle, German researcher claims". The Guardian. Retrieved 2016-08-07.
- "The Death of Bruce Lee". Find a Death. Retrieved 2012-02-19.
- Li Zhisui (2010). Private Life Of Chairman Mao: The Memoirs of Mao's Personal Physician. Random House. p. 100. ISBN 9781407059228.
- Will KW, Liebherr JK, Maddison DR, Galián J (2005). "Absence asymmetry: the evolution of monorchid beetles (Insecta: Coleoptera: Carabidae)". J. Morphol. 264 (1): 75–93. doi:10.1002/jmor.10319. PMID 15732050.