Cryptorchidism in common eutherian mammals.

The research article provides a comprehensive study on cryptorchidism, a condition where one or both testes fail to descend into the scrotum in common eutherian mammals. The study introduces a unified interpretation of testis descent and emphasizes the importance of accurate terminology.

Understanding Cryptorchidism

• According to the research, the primary fault of Cryptorchidism lies in the testis itself. The testis is relocated to the scrotum in a three-step process: abdominal translocation, transinguinal migration, and inguinoscrotal migration. Specifically, cryptorchidism is characterized and understood through the following key factors:
  • The testis initially gets relocated near the internal inguinal ring as the abdominal cavity expands away. This is marked by a slight downward migration process.
  • Following this, the cauda epididymidis and testis move through the abdominal wall in a process known as transinguinal migration.
  • Finally, the cauda epididymidis and testis are moved to the bottom of the scrotum in a process known as inguinoscrotal migration.

Contribution of Insulin-Like Peptide 3 and Testosterone

• During the first phase of testis relocation, the gubernaculum (an anatomical structure in males that guides the testis descent) enlarges under the stimulation of insulin-like peptide 3, helping to anchor the testis in place. Concurrently, testosterone plays an important role in the masculinization of the genitofemoral nerve (a nerve in the pelvic region).
• The research also reveals that testosterone is not necessary for the correct migration of testes to the scrotum, but typically stimulates the growth of the vaginal process and provides directional guidance to the gubernaculum.

Rate of Cryptorchidism in Various Species

• The occurrence of the condition of cryptorchidism varies across species. It is found to be more common in companion animals, pigs, and humans with 2-12% occurrence rate than in cattle or sheep, which have an occurrence rate less than or equal to 1%.
• Interestingly, the location of the abdominal testes also differs among species. They are predominantly found in cats, dogs, and horses. Inguinal testes are more common in rabbits and horses but can sometimes be found in cats and dogs. Subcutaneous (s.c.) testes are found in cattle, cats, and dogs, but are most common in humans.