Testicular feminization syndrome in a mare.

This research studied a mare diagnosed with testicular feminization syndrome, a condition typically characterized by high testosterone levels, male-like behavior, and infertility due to an abnormality in androgen receptors. A surgical procedure to remove hypoplastic testicles from the mare resolved its aggressive behavior, and a chromosomal evaluation revealed an unusual 64X,Y karyotype.

Study Background and Objectives

• The study was based on a specific case of a mare which exhibited stallion-like, aggressive behavior and had a history of infertility. These symptoms along with high testosterone concentrations suggested testicular tissue presence in the mare.
• The primary objectives of the research were to diagnose the medical condition causing these symptoms, perform appropriate surgery, and assess its results. Additionally, a chromosomal evaluation was undertaken to identify any underlying genetic anomalies.

Research Methods and Findings

• Initial examinations involved transrectal ultrasonography of ovarian-like structures, which revealed typical appearances of testicular tissue.
• Despite the mare exhibiting external female genitalia, her internal reproductive organs were abnormal with her vagina ending in a blind sac, and no cervix or uterus found.
• Surgery was carried out, and the structures removed from the abdominal cavity were identified as being underdeveloped testicles or hypoplastic testicles.
• Following the surgical procedure, the aggressive behavior exhibited by the mare resolved completely.
• A chromosomal assessment revealed that the mare had a 64X,Y karyotype, which is typically found in males.

Conclusions and Implications

• The research concluded that the mare was diagnosed with testicular feminization syndrome. This syndrome is associated with an abnormality in androgen receptors leading to insensitivity of reproductive tissues to androgens during development. This can lead to the development of external female genitalia while releasing high testosterone levels from the developing testicles.
• Testicular feminization syndrome is not commonly diagnosed in horses. Still, it should be considered as a potential cause when examining overly aggressive mares suffering from infertility.
• This research contributes to enhancing the understanding of testicular feminization syndrome in horses and potentially helps veterinarians diagnose and treat this condition in future cases.