A case of equine cryptorchidism with undetectable serum anti-Müllerian hormone.

This research article examines a unique case of a Thoroughbred racehorse that has bilateral cryptorchidism, indicated by no visible testes, yet has undetectable levels of serum anti-Müllerian hormone (AMH), a hormone that is usually present in intact and cryptorchid stallions.

Understanding Cryptorchidism

• Equine cryptorchidism is a medical condition in which a male horse’s one or both testes fail to descend. In this specific case, the horse presented with bilateral cryptorchidism – both testes were undescended.
• This abnormality is usually identified by the absence of visible testes and detectable levels of serum anti-Müllerian hormone (AMH) in the blood, which is secreted by Sertoli cells in the testes.
• In this study, however, the researchers encountered an exceptional case where the cryptorchid horse had undetectable levels of serum AMH in his blood.

Hormonal and Genetic Analysis

• To further confirm the horse’s status, the researchers conducted a hormonal stimulation test using human chorionic gonadotrophin (hCG). The response to this test indicated that the horse was gelded, meaning both its testes had been surgically removed.
• A comprehensive chromosomal and genetic analysis suggested that, contrarily, the horse was a genetically intact stallion (X/Y), indicating the presence of functional male sex chromosomes.
• However, when physically examined, only one small and degenerated testis was found inside the horse’s abdomen.

Reasons Behind the Anomaly

• The researchers believe that the low numbers of Sertoli and Leydig cells, which are primarily involved in producing the hormones, could be the reason for the horse’s undetectable levels of serum AMH and the negative response to hCG stimulation.
• It is the shortage of these cells that might have resulted in the horse’s unique presentation of cryptorchidism.
• The study’s conclusions highlight the potential complexities that can occur within equine cryptorchidism.

Significance of the Study

• This research is important because it reports an unorthodox case of an AMH-undetectable cryptorchid stallion, providing further insights into the complexity and variability of equine cryptorchidism.
• The study might refine and enhance diagnostic techniques and treatments for horses affected by cryptorchidism in the future.