A closer look: Cushing's Disease (Hyperadrenocorticism) in Cats
Cortisol is a steroid hormone that suppresses inflammation. It is manufactured by and stored in the adrenal glands (which are located in the kidneys) and is naturally released in times of stress. Cortisol production is regulated by the pituitary gland in the brain.
Cushing’s syndrome can be classified into:
ACTH-dependent Cushing's syndrome involves the pituitary gland. Adrenocorticotropic hormone (ACTH) is produced by the pituitary gland to stimulate adrenal gland activity. When small pituitary gland tumors increase the production of ACTH, cortisol levels go up without regulation.
ACTH-independent Cushing's syndrome involves the adrenal gland. This occurs when the adrenal cortex produces an excess of cortisol hormone independently from the pituitary gland. Adrenal tumors are the most common cause of this form of Cushing's syndrome.
Iatrogenic Cushing's syndrome is caused by prolonged or high-dose administration of steroid-containing drugs.
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Elevated levels of cortisol cause a number of symptoms that significantly decrease quality of life. Cushing’s syndrome is rare in cats, but if left untreated it can be life-threatening, as such it must be treated as an emergency.
Pituitary gland tumors are the most common cause of feline Cushing's syndrome.
Middle-aged and older cats are more likely to develop Cushing’s syndrome due to a tumor. Cats of any age receiving high doses of steroids are at risk of developing Cushing’s disease spontaneously.
Cushing's syndrome is caused by excessive amounts of cortisol hormones in the animal's system.
The excessive production of steroid hormones can be caused by one of three underlying conditions:
- Pituitary gland tumor
- Adrenal gland tumor
- Excessive administration of steroid-containing drugs
Testing and diagnosis
Cushing’s syndrome is very rare in cats. It requires specialized blood testing to diagnose. Common diagnostic tools include:
- Blood tests, including cortisol levels and hormone response tests
- Hormone level test
- Diagnostic imaging
Treatment depends on the underlying cause.
Steps to Recovery
Treatment for ACTH-dependent hyperadrenocorticism involves:
- Radiotherapy medication
- Medication to reduce the production of cortisol
Treatment for ACTH-independent hyperadrenocorticism involves the surgical removal of one or both adrenal glands. Surgery is the only treatment option for adrenal gland tumors, as they do not respond to chemotherapy.
Treatment for iatrogenic hyperadrenocorticism involves weaning off the steroid-containing medication.
The prognosis for Cushing's syndrome varies depending on the type. Once diagnosed, the animal may require life-long medication and monitoring.
Cushing’s syndrome is not contagious.
Cushing’s syndrome is unpreventable. Cats with Cushing’s syndrome are likely to suffer from diabetes mellitus. Testing for Cushing’s syndrome is advised for diabetic cats.
Is Cushing's Disease (Hyperadrenocorticism) in Cats common?
Cushing’s disease is a rare condition in cats.
- Weaning off steroid-containing medication
- Cortisol reducing medication