Physical, behavioral, endocrinologic, and cytogenetic evaluation of two Standardbred racehorses competing as mares with an intersex condition and high postrace serum testosterone concentrations.
Abstract: 2 Standardbred racehorses that had been winning races while competing as mares underwent postrace drug testing and had serum testosterone concentrations above the acceptable limit for female racehorses. Results: Initial physical examinations by the referring veterinarian revealed ambiguous external genitalia and suspected intra-abdominally located testes leading to a preliminary diagnosis of male pseudohermaphroditism. Horses were referred for further evaluation of sex. Physical examination of the external genitalia confirmed the findings of the referring veterinarian. Transrectal palpation and ultrasonography revealed gonads with an ultrasonographic appearance of testes. On cytogenetic analysis, both horses were determined to have a 64,XY karyotype and 8 intact Y chromosome markers and 5 SRY gene markers, which were indicative of a genetic male and confirmed an intersex condition. Additionally, both horses had some male-type behavior and endocrinologic findings consistent with those of sexually intact males. Results: Taken together, these findings confirmed that both horses were male pseudohermaphrodites. Both horses returned to racing competition as males. Conclusions: As of October 1, 2008, the Pennsylvania Horse and Harness Racing Commissions implemented a postrace drug testing policy that included analysis of blood samples for anabolic and androgenic steroids and set maximum allowable concentrations of testosterone for racing geldings and females. Within 8 months of initiation of this drug testing policy, the 2 horses of this report were identified as having an intersex condition. This raises the possibility that intersex conditions may be more common in racing Standardbreds than was previously suspected.
Publication Date: 2011-03-16 PubMed ID: 21401432DOI: 10.2460/javma.238.6.751Google Scholar: Lookup
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- Journal Article
Summary
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The research focuses on two Standardbred racehorses identified as females, which showed high postrace serum testosterone concentrations and displays of male behavior. Upon physical, endocrinologic, and cytogenetic evaluation, it was confirmed that they were pseudohermaphrodites, genetically male but possessing ambiguous external genitalia. This finding led to speculation that intersex conditions may be more prevalent in racing Standardbreds than previously thought.
Initial Situations and Observations
- The racehorses, initially recorded and competing as mares, displayed serum testosterone concentrations exceeding the acceptable limit for females in postrace drug tests.
- Initial physical evaluation by a veterinarian revealed indeterminate external genitalia and the possibility of testes located intra-abdominally, suggesting male pseudohermaphroditism.
Further Examination
- Both horses were referred for further sex evaluation. Further physical examination of external genitalia validated initial findings.
- Transrectal palpation and ultrasound examinations revealed gonads with an appearance consistent with testes.
Cytogenetic Analysis
- Upon cytogenetic profiling, both horses exhibited a 64,XY karyotype within their cells, which associates with male sex determination in mammals.
- The horses showed eight intact Y-chromosome markers and five SRY gene markers, indicating they were genetically male and confirming an intersex condition.
Behavioral and Endocrinologic Findings
- Both horses displayed some male-type behaviors and endocrinologic characteristics common to sexually intact males.
Final Conclusion
- These diverse evaluations certified both horses as male pseudohermaphrodites. They returned to racing, this time classified as males.
- The Pennsylvania Horse and Harness Racing Commissions, in October 2008, implemented a postrace drug testing policy, which included scanning blood samples for steroids and setting a maximum tolerable testosterone concentration for geldings and females.
- As a result of this new policy, within 8 months these two racehorses were declared to have intersex conditions, raising the possibility of a higher prevalence of such conditions in Standardbred racehorses than initially suspected.
Cite This Article
APA
Knobbe MG, Maenhoudt C, Turner RM, McDonnell SM.
(2011).
Physical, behavioral, endocrinologic, and cytogenetic evaluation of two Standardbred racehorses competing as mares with an intersex condition and high postrace serum testosterone concentrations.
J Am Vet Med Assoc, 238(6), 751-754.
https://doi.org/10.2460/javma.238.6.751 Publication
Researcher Affiliations
- Department of Clinical Sciences, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, PA 19348, USA.
MeSH Terms
- Animals
- Behavior, Animal
- Disorder of Sex Development, 46,XY / diagnosis
- Disorder of Sex Development, 46,XY / veterinary
- Female
- Horses / genetics
- Horses / physiology
- Karyotyping
- Male
- Sports
- Testosterone / blood
Citations
This article has been cited 2 times.- Bugno-Poniewierska M, Raudsepp T. Horse Clinical Cytogenetics: Recurrent Themes and Novel Findings. Animals (Basel) 2021 Mar 16;11(3).
- Scholtz EL, Krishnan S, Ball BA, Corbin CJ, Moeller BC, Stanley SD, McDowell KJ, Hughes AL, McDonnell DP, Conley AJ. Pregnancy without progesterone in horses defines a second endogenous biopotent progesterone receptor agonist, 5α-dihydroprogesterone. Proc Natl Acad Sci U S A 2014 Mar 4;111(9):3365-70.
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