The adrenal glands are located just in front of the kidneys. The adrenal gland has 2 parts—the cortex and the medulla.
The adrenal cortex is subdivided into 3 layers, and each layer produces a different set of steroid hormones. The outer layer produces the mineralocorticoids, which help to control the body’s balance of sodium and potassium salts. The middle layer produces glucocorticoids, which are involved in metabolizing nutrients as well as in reducing inflammation and immune responses. The inner layer produces sex hormones such as estrogen, progesterone, and androgens.
The adrenal medulla plays an important role in response to stress or low blood sugar (glucose). It releases epinephrine (sometimes also called adrenaline) and norepinephrine, both of which increase heart output, blood pressure, and blood glucose, and slow digestion.
Addison disease, also referred to as hypoadrenocorticism, is caused by a deficiency of adrenal gland hormones. It is rare in cats. The cause is usually not known, but an autoimmune condition in which the body destroys some of its own tissue is likely. The adrenal gland can also be destroyed by other conditions, including cancer in other parts of the body. Secretion of aldosterone, the main mineralocorticoid hormone, is reduced, which affects the levels of potassium, sodium, and chloride in the blood. Potassium gradually builds up in the blood and, in severe cases, may cause the heart to slow down or beat irregularly.
Signs of Addison disease include loss of appetite, lethargy, dehydration, and a gradual loss of body condition. Vomiting and diarrhea may be noted. Although signs can be hard to identify while Addison disease is developing, severe consequences, such as shock and evidence of kidney failure, can develop suddenly (called an adrenal crisis).
A veterinarian can make a tentative diagnosis based on the history, signs, and certain laboratory abnormalities, such as very low levels of sodium and very high levels of potassium in the blood. The diagnosis is confirmed by specific evaluation of adrenal function.
An adrenal crisis is a medical emergency and requires treatment with intravenous fluids to restore levels of body fluids, salt, and sugar to normal. Hormone replacement treatment can often be started while the animal is being stabilized. For longterm treatment, replacement hormones can be given by mouth or injection. The cat should be monitored regularly to assess response to treatment and adjust dosages if needed. Stress can trigger an adrenal crisis, so your veterinarian may recommend dose adjustments during stressful situations (for example, the introduction of a new pet or a household move).