Clinical, morphological and endocrinological aspects of cryptorchidism in the horse.

This research focuses on studying the clinical, histological, and hormonal aspects of cryptorchidism in horses. It was found out that most of the retained testes were located in the inguinal canal and left abdominal region with right inguinal retention seen decreasing with age. Although cryptorchid testes had normal Leydig cells and stalled spermatogenesis, plasma testosterone concentrations were similar amongst normal stallions and unilateral cryptorchids. Plasma oestradiol-17beta levels were found to be lower in unilateral cryptorchids than in stallions.

Study Objective and Method

• The main purpose of this research was to garner a deeper understanding of equine cryptorchidism. This condition refers to the incomplete descent of one or both testes into the scrotum before birth, resulting in them being retained in the abdominal cavity or inguinal canal. The study further explored the location of retention, age-related changes, and certain hormonal aspects associated with this condition.
• Researchers gathered and analysed clinical, histological and hormonal data from 205 horses suffering from cryptorchidism to draw their conclusions.

Testes Location and Age-Related Findings

• Among the cryptorchid horses, unilateral and bilateral retention of testes was mostly observed in the inguinal canal – the passage in the anterior abdominal wall through which a testis descends into the scrotum. It was found out that the ratio of inguinal vs abdominal retention seemed to decrease with advancing age of the horse.
• In cases of unilateral cryptorchidism, there was a notable preference for left abdominal retention. Inguinal cryptorchids had retention occurring equally on both sides.
• Interestingly, the researchers noted a decrease in right inguinal retention with advancing age.

Histological and Hormonal Findings

• Merely looking at the cells under a microscope, the testes seemed to have normal Leydig cells – cells that produce testosterone – but had arrested or stopped spermatogenesis, which is the process of sperm cell development.
• Even with cryptorchidism, horses were found to have plasma testosterone concentrations similar to those of normal stallions. This was even the case for unilateral cryptorchids that had the scrotal testis removed.
• In terms of plasma oestradiol-17beta levels, usually associated with sexual and reproductive functions, the study found these to be lower in horses with unilateral cryptorchidism compared to normal stallions.