Cushing's Disease in Cats: An Overview
Dog Breeds
Cushing's Disease is an umbrella term that refers to a number of conditions that occur when an animal is exposed to too much steroid hormone (called glucocorticoids). Cushing's disease occurs when the body produces excessive amounts of steroids, usually as a result of a pituitary gland problem, adrenal gland tumor, or too much steroid medication.
Read More >
Definition
Hyperadrenocorticism, commonly called “Cushing's Disease,” is a disorder of excessive steroid secretion by the adrenal glands. In the vast majority of cases, this disease involves excess production of cortisol.
How Cushing’s Disease Affects Cats
Hyperadrenocorticism is uncommon in cats. When it does occur, it has many of the clinical characteristics of Cushing’s in dogs, but there are some very important differences.
Feline Cushing’s is a disease of older, primarily mixed-breed cats of either gender. Unlike canine Cushing’s, this disease in cats is strongly associated with diabetes mellitus. The most common initial clinical signs are increased water intake (polydipsia) and the resulting increase in urination (polyuria), together with increased appetite/eating (polyphasia). These signs are more likely caused by the diabetes than by the hyperadrenocorticism. Other signs during the early course of the disease are often subtle and nondiagnostic. Diabetes is typically diagnosed first. Cats with Cushing’s will not respond normally to insulin therapy and, over time, will become progressively debilitated despite appropriate administration of potent insulin. They will lose weight relentlessly and develop severe cachexia (affected dogs tend to gain weight). Their skin will atrophy and become extremely fragile, thin, bruised, easily torn and ulcerated. Skin lesions are often noticed (or actually occur) during grooming or when the cat is handled for physical examination at the veterinary clinic. Other possible signs are weakness, lethargy, muscle atrophy, hair loss, diarrhea, vomiting, pendulous abdominal enlargement, poor wound healing and an overall unkempt appearance. Several, but not all, of these signs usually appear together.
Cushing's disease is very slowly progressive, and very few owners notice that there is anything “wrong” with their cat until the disease is advanced. Frequently, owners attribute the vague clinical signs to the normal effects of aging.
Causes of Feline Cushing’s Disease
Hyperadrenocorticism can be either pituitary-dependent (PDH) or adrenocortical-dependent (caused by an adrenal tumor, “ATH”). It is extremely rare for Cushing’s in cats to be caused by iatrogenic administration of steroid drugs. Most affected cats have PDH; those with ATH have either benign adenomas or malignant adenocarcinomas, with roughly equal distribution. In cats with pituitary-dependent hyperadrenocorticism, excess secretion of adrenocorticotropic hormone (ACTH) from the pituitary gland stimulates the adrenal glands to produce excessive amounts of cortisol and causes the adrenal glands to enlarge (adrenal hypertrophy). Cats with functional adrenal tumors produce and secrete abnormally large amounts of cortisol autonomously.
Preventing Hyperadrenocorticism in Cats
There is no way to prevent hyperadrenocorticism in cats. It occurs for reasons as yet unknown.
Special Notes
Treatment of Cushing's disease requires reducing or preventing the excessive production of steroids. Surgical excision of affected adrenal glands is possible and usually quite successful. A number of drugs also are available to either inactivate the adrenal glands or to otherwise regulate and normalize the amount of steroid production.
The prognosis for cats with hyperadrenocorticism is guarded to poor. While surgical removal of affected adrenal glands is possible and has the potential to be quite successful, it requires prior correction of the cat’s debilitated condition, a very skilled surgeon and owner commitment to medical management of the prospective steroid deficiency.
Diagnosis and Tests