Tumors of the Endocrine Glands in Cats

Tumors that secrete cortisol are the most common and a third of these tumors are malignant (cancerous). Metastasis (spreading) of cancer from these tumors is uncommon, but can happen, usually to the lymph nodes. Sex hormones, aldosterones and, in very rare cases, catecholamines can be secreted from tumors of the endocrine glands. Often another disease will show up secondary to the tumor growth and cause symptoms. These tumors can be life threatening and veterinary attention is needed.

The endocrine system is made up of a group of glands that release hormones into the bloodstream. Sometimes these glands start to secrete too many hormones and tumors begin to form. This condition is rare in cats, happening to about 0.03 percent of cats seen in clinics. Once the gland has a tumor growth, it may or may not continue to produce hormones and will be labelled as functional or nonfunctional. Hormones are needed to help the cat’s body operate properly.

While there are different types of hormones that can be secreted to cause these tumors, almost all of the symptoms are shared. Symptoms typically worsen with the progression of the tumors. Symptoms include:

• Relaxed abdomen muscles (pot belly)
• Muscle atrophy
• Muscle pain
• Lethargy
• Fragile skin
• Pussing or abscessed skin
• Seborrhea Sicca (dry skin)
• Dull coat
• Alopecia (hair loss)
• Weakness
• Vomiting
• Diabetes Mellitus
• Polyuria (excessive urination)
• Polydipsia (excessive thirst)
• Polyphagia (excessive appetite)
• Dehydration
• Stiffness 
• High blood pressure
• Blindness

It is believed that a chain of events may cause endocrine gland tumors to develop. All known contributors are as follows:

• Hormonal excess
• Biochemical changes
• Ionizing radiation
• Metabolic disorders
• Goitrogenic substances or foods
• Prolonged hormone stimulation
• Disruption of hormone pathways

Your veterinarian will require your cat’s complete medical history. From there, tests will be performed to measure the amount of hormones present in your cat. Often the vet will test the pituitary-adrenocortical axis for ACTH (adrenocorticotropic hormone) concentrations. This can lead the vet to a diagnosis of hyperadrenocorticism (overproduction of cortisol). 

The veterinarian may choose to test for elevated amounts of serum aldosterone concentration paired with low plasma renin concentration. If this is found, hyperaldosteronism (overproduction of aldosterone) can be diagnosed.

To diagnose the overproduction of sex hormones, the amount of concentration of the hormones is recorded before and after ACTH stimulation. 

Once the hormone has been identified, an abdominal ultrasound, CT scan or MRI will be needed. This can confirm the presence and the size of endocrine gland tumors. After the number, location and size of tumors has been found, appropriate treatment can be recommended.

There are both surgical and nonsurgical options available for treating tumors of endocrine glands, depending on the location and severity of the condition. Treatment options are listed below.

Adrenalectomy 

Instead of removing the tumors alone, often a complete removal of the gland is performed. Either one or both of the adrenal glands can be excised. General anesthesia is used. This treatment has the highest success rate, and can even cure the cat if no spreading has already occurred. The surgery itself does have risks, and not all cats are appropriate candidates. Hormone replacement supplements will be needed for at least 2 months post surgery.

Medication 

If the cat has been diagnosed with hyperadrenocorticism but is a poor surgical candidate, medications such as trilostane or mitotane may be prescribed for long-term management or palliative care. These medications may also be given to cats preparing to have surgery.

Supplements 

In cases of hyperaldosteronism, parenteral or oral potassium supplements, such as potassium gluconate or spironolactone  may be given for long term care. These supplements are often paired with the correction of fluid deficiencies and a pH balance of the cat. Sometimes these treatments alone can be used indefinitely instead of surgery.

Radiotherapy 

Radioactive iodine can be used to destroy overactive thyroid glands in some cases. 

If the cat has undergone surgery, prevent it from licking the incision. Watch daily for any signs of infection. If swelling or bleeding occur, a return trip to the veterinary clinic or animal hospital is needed. Verify that your cat is passing both urine and feces in the first week at home.

If the cat is taking hormone replacements, monitor if any side effects are developing. It is important to ask your vet to periodically retest the cat for appropriate hormonal dosage. In some cases, the cat will make a full recovery. More often than not, life-long treatment will be necessary.