Addison's Disease in Cats

The adrenal glands in a feline are located in front of both the right and left kidneys. Each adrenal gland is made up of two crucial parts; the cortex (outer layer) and the medulla (center). The adrenal cortex itself has three layers that each produce a different set of steroidal hormones. The outermost layer controls the body’s balance of potassium salts and sodium by releasing mineralocorticoids. The middle layer of the cortex is responsible for metabolizing nutrients and reducing inflammation in the body by releasing glucocorticoids. Finally, the inner layer of the cortex regulates the reproductive cycle by releasing progesterone and estrogen. The adrenal cortex is vital in controlling the body’s response to low glucose levels and stress by releasing norepinephrine in addition to epinephrine. These hormones are also vital in slowing digestion and regulating blood sugar levels, blood pressure, and cardiac output. 

Damage to either of the cat’s adrenal glands due to disease or immune-mediated conditions will result in a termination of the adrenal gland function. Without the release of vital life-supporting hormones from the adrenal glands, potassium levels build up in the blood, resulting in a low heart rate followed by severe health conditions. 

Addison’s disease in cats is a potentially life-threatening disorder caused by an inadequate amount of hormones produced by two small glands that sit just in front of the feline’s kidneys. Addison’s disease is also referred to as hypoadrenocorticism, as it is the corticosteroids that are deficient in this rare feline disease. Cortisol is a vital for life as it provides several important functions including the release of glycogen, the conversion of proteins to energy, as well as immunosuppressant and anti-inflammatory qualities. A feline with Addison’s disease will appear weakened, depressed, and have a low body weight. Without veterinary medical treatment, the feline’s body will not be able to carry out routine organ functions and the condition soon becomes an emergency situation. 

In most Addison’s disease cases, clinical signs of the disease are usually noted within days of damage to the feline’s adrenal glands. However, symptoms can also appear over a monthly period, which are not limited to: 

• Hyperkalemia (elevated blood potassium levels)
• Weight loss
• Weakness
• Shaking 
• Tremors 
• Listlessness
• Lethargy
• Hypoglycemia (low blood sugar/glucose)
• Gastrointestinal irregularities including diarrhea and vomiting 
• Depression
• Dehydration 
• Arrhythmias (irregular heart beat)
• Anorexia (loss of appetite) 

Addison’s disease in cats is caused by deficient levels of hormones regularly produced by the adrenal glands. The reason as to why the adrenal glands discontinue hormone production is not known, but some diseases are linked to this rare feline condition. In many cases, the immune system, which normally protect the body from illness, begins to attack itself and destroys the tissues of the adrenal glands. This abnormality of the immune system attacking the body is referred to as immune-mediated disease, which in itself has no known cause. Other invasive diseases such as cancer or infections, destroy the tissues of the adrenal glands and can cause the feline to develop Addison’s disease.

Addison’s disease in cats mimics the symptoms of a number of other feline health conditions, so the symptoms alone will not be enough to diagnose a cat with hypoadrenocorticism. Therefore, your veterinarian will likely request a blood test to identify any abnormalities that could link the feline’s condition to the disease. The evidence of very high potassium level in the blood, as well as very low sodium levels, will be a clue that would suggest Addison’s disease. However, the only sure test of Addison’s disease is the test that has the ability to measure the adrenal glands’ response to adrenocorticotropic hormone, known as the ACTH stimulation test. The adrenocorticotropic hormone is produced by the pituitary gland produced to stimulate the release of adrenal gland hormones. Therefore, if the doctor can see that the pituitary gland can trigger a response in the adrenal glands, Addison’s disease can likely be ruled out. 

Initially, your feline will likely need to be hospitalized as the majority of patients are admitted to the veterinary clinic with what is called an adrenal crisis. Felines are usually severely dehydrated and require stabilization therapy of intravenous fluids containing electrolytes. Once the feline is stable, he or she will need to have hormone replacement medications substitute the absent adrenal hormones. The medication can be administered by mouth or as an injection every day for the remainder of your cat’s life.

A feline with Addison’s disease will need to be given hormone replacement therapy drugs for the rest of his or her life, but they can be administered in the comfort of your own home. As soon as the absent hormones are substituted with adequate medication, the cat will be restored to her normal self and can live a long, happy life.