When the gonads are not producing enough hormones, the cat will be described as having hypogonadism. Something may be deterring the gonads themselves from operating correctly, or there may be an issue with the glands that signal the gonads to produce. Hormonal pathways can become blocked or damaged leading to this problem. Sometimes the issues that arise are in direct relation to the genitals and reproductive system, but they can also manifest into skin and growth problems. Veterinary treatment can be very effective at alleviating symptoms and restoring the cat's quality of life.

Sex hormones in the body are responsible for regulating several different functions, including development and growth. These hormones include estrogen, testosterone, progesterone, androgen and deoxycortisol, among others. They are secreted by a cat’s endocrine gonad glands, which are signaled to work by pituitary or adrenal glands. When something interferes with this process, many other issues can occur.

Often symptoms may arise after an early castration or ovariohysterectomy have been performed (also known as routine spay and neutering). Intact cats can be deficient as well. Symptoms are as follows:

Problems within the cat from birth, along with external circumstances, can be the cause of deficiencies of the sex hormones. There is substantial research suggesting that the age at which a cat is castrated or spayed can affect the production of the gonad glands. Known causes include:

At a veterinary appointment, you will be asked for the cat’s full medical history. The veterinarian will perform a complete physical exam. If your cat is an intact male, the vet will palpate the testes with or without calipers to gauge size. The overall size and weight of the cat will be noted and compared with breed averages. If the cat has been fixed, the vet will need to know at what age.

Blood work will be needed, including a complete blood count and a biochemical profile to rule out any other possible causes. Hormone levels should be checked to detect abnormal lows. Adrenocorticotropic hormone (ACTH) can be used to stimulate the production of glands while the responses are monitored. Histological examination of skin scrapings can also reveal the absence of necessary hormones. X-rays and ultrasounds can be used to confirm and locate tumors on the endocrine glands. Feline leukemia virus should be tested for, as it is also present in many hormonal complications.

Depending on the underlying cause of the deficiency, various treatments may be administered to restore hormonal function within the cat. Most sex hormone deficiencies are not life threatening, however, proper treatment can improve the cat’s overall health and help identify other health problems. 

In most cases of a hormone deficiency, hormones can be injected or ingested on a regular basis to compensate. Supplementation of sex hormones can come with risks, so sometimes symptoms can be alleviated with the administration of other hormones. This treatment works in the case of alopecia, which can be relieved with thyroid hormone doses. These treatments generally have to continue throughout the cat’s life.

When a tumor is blocking the function of an endocrine gland, surgical removal may be necessary to restore production and secretion of hormones. Depending on the location of the tumor, higher risks can be involved. General anesthesia is required for the surgery, along with significant at-home care. 

Certain conditions that can develop from sex hormone deficiency may need to be treated with ongoing medication, such as in the case of urethral sphincter mechanism incompetence (USMI). In this rare condition, which develops from too little estrogen, phenylpropanolamine may be prescribed to restore some urethral pressure to stop incontinence.

If infection has affected the pituitary, adrenal, or gonad glands, antibiotics will be needed to kill off the bacteria causing the infection. Also, after surgery, antibiotics will be prescribed in the weeks after the procedure to ward off infection.

Regular visits to the vet will be needed to continually test hormone levels for proper dosing and to monitor the progression of any side effects. Things to watch out for that can develop with sex hormone supplementation are behavioral changes, diabetes mellitus, mammary gland tumors, bone marrow toxicity and liver toxicity. If you suspect any of these symptoms are present, immediately bring your cat back to the clinic. 

If surgery was used to remove a tumor on an endocrine gland, there is a chance that the gland can recover and return to regular hormone production. This does not occur often, and in most treatments, hormones must be given throughout the cat’s life.