Small Sized Testes in Cats

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Testicular Degeneration and Hypoplasia in Cats

Cats with smaller than normal testes are often not diagnosed until they have attempted to breed and have been unsuccessful, leading to a veterinary check. There are different conditions that can lead to this disorder: underdevelopment or incomplete development of the testes, also known as hypoplasia; and degeneration of the testes, which refers to the loss of potency after the stage of puberty has arrived. The latter condition is more typical in older cats.

Both of these conditions can be due to a condition that was present at birth -- congenital -- or can be due to some other cause that takes place after birth. The congenital forms are usually related to genetic abnormalities that have been inherited by the parent, but may also be due to something that occurred while the kitten was in utero, such as exposure to radioactive substances or other toxins.

Cats of any age or breed are predisposed to these conditions, but hypoplasia is most commonly seen in young cats, and degeneration is more common in older cats.

Symptoms and Types

In addition to abnormally small testes, infertility is the single most common symptom of these conditions. Semen analysis will show a low sperm count (oligospermia) or an absolute absence of sperms (azoospermia) in the seminal fluid is usually reported.


  • Hypoplasia
  • Genetic
  • Radiation exposure
  • Metal toxicity, including lead
  • Chemical toxicity
  • Other toxins
  • Adverse drug reaction (e.g., antifungal drugs)
  • Exposure to heat
  • Hormone imbalance
  • Tumor of the pituitary gland
  • Increasing age
  • Degeneration of the testicular sacs
  • Injury, trauma
  • Inflammation of the testes (orchitis)



Mostly cats with these conditions are presented to their veterinarians with an owner's complaint of infertility. You will need to give your doctor a complete known health history, including any such problems that were present in the previous generations of your cat's familial line and any trauma or injury that may have affected your cat's scrotum.

Your veterinarian will thoroughly examine the scrotal region and should be able to immediately ascertain whether they are of normal size or are smaller than what they should be for your cat's breed, size and age. A finding of abnormal size is enough to urge your veterinarian to conduct further tests in order to differentiate testicular degeneration from hypoplasia. An ultrasound image of the testes is usually done to confirm the visual diagnosis of smaller than normal testes.

Your veterinarian will also take a semen sample for laboratory testing, to check for abnormal cell development and to do a standard sperm count. The sperm count will evaluate the number of viable sperm cells in your cat's semen. If it appears to be called for, under the circumstances, a small tissue sample may also be taken from the testicular sac, using a fine needle, to be sent to the laboratory for further evaluation.

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