Cushing’s disease, also called hyperadrenocorticism, happens when the body is exposed to too much cortisol for too long. In pets, this condition is much more common in dogs than in cats, and most naturally occurring cases are caused either by a pituitary tumor that stimulates excess cortisol production or by an adrenal tumor that produces cortisol directly.
What Cushing’s Disease Means
Cortisol is a normal hormone that helps the body respond to stress and regulate metabolism, but excessive amounts over time can affect many organs and body systems. In dogs and cats, veterinarians usually divide Cushing’s syndrome into pituitary-dependent disease, which accounts for about 80% to 85% of reported cases, and adrenal-dependent disease, which accounts for about 10% to 15% of cases. In dogs, naturally occurring Cushing’s syndrome is most often ACTH-dependent and usually caused by a pituitary tumor, while exogenous steroid use can also cause iatrogenic disease (e.g. a patient being on a corticosteroid such as prednisolone for too long).
Which Pets Are Affected
Cushing’s syndrome tends to occur in middle-aged to older animals. It can affect any breed or size of dog, although adrenal-dependent disease tends to be seen more often in larger dogs and many pituitary-dependent cases are reported in small breeds. Cats can develop Cushing’s disease too, but it is an infrequent diagnosis and most feline cases are also pituitary-dependent.
Common Signs in Dogs
In dogs, the most common signs include drinking more water, urinating more, eating more, a pot-bellied or pendulous abdomen, panting, muscle wasting, and skin or coat changes such as hair loss, thin skin, or recurring skin infections. Many affected dogs also have systemic hypertension. Because these signs can develop gradually, owners sometimes mistake them for normal aging and do not realize the pattern points to an endocrine disorder.
Common Signs in Cats
In cats, Cushing’s disease is rare and often occurs along with diabetes mellitus that is difficult to regulate. One of the most distinctive feline features is markedly thin, fragile skin that can tear easily, sometimes called feline fragile skin syndrome. Cats may also show increased thirst and urination, but these signs are often influenced by concurrent diabetes.
How Veterinarians Diagnose It
Diagnosis starts with the pet’s history, physical examination, and routine laboratory testing, but endocrine testing is usually needed to confirm the disease. In dogs, the low-dose dexamethasone suppression test is considered the screening test of choice because of its high sensitivity, and in many cases it can also help distinguish pituitary-dependent from adrenal-dependent disease. Abdominal ultrasound or CT is also important because imaging helps identify whether both adrenal glands look symmetrically enlarged, which supports pituitary-dependent disease, or whether a unilateral adrenal mass is present, which supports adrenal-dependent disease.
In cats, diagnosis can be more challenging because routine laboratory abnormalities are less consistent and many cats have other illnesses at the same time. The low-dose dexamethasone suppression test is considered the most reliable diagnostic test in cats, and cats require a higher dexamethasone dose than dogs for that test. AAHA (American Animal Hospital Association) also notes that the ACTH stimulation test is not recommended as a diagnostic tool in cats because its sensitivity for feline hyperadrenocorticism is poor. The ACTH stimulation test is a lab test often used to diagnose both Cushing’s disease and Addison’s disease.
Treatment Options
Treatment depends on the cause of the disease and the overall health of the pet. For adrenal-dependent disease, adrenalectomy, or surgical removal of the affected adrenal gland, is considered the treatment of choice, although case selection is important because perioperative risk can be significant. When surgery is not possible, medical management may still help, and in dogs both trilostane and mitotane have been used successfully in some cases.
For canine pituitary-dependent Cushing’s disease, medication is commonly used to control cortisol production and improve quality of life. In cats, medical therapy is often less predictable and response to trilostane or mitotane is generally poorer than in dogs. Because of these differences, long-term plans for cats usually require especially close monitoring and discussion with a veterinarian or veterinary internal medicine specialist.
Monitoring and Follow-Up
Cushing’s disease is usually managed over time rather than fixed with a single visit. Pets receiving treatment need follow-up examinations, repeat laboratory testing, and dose adjustments to balance symptom control with the risk of suppressing cortisol too much. Owners should promptly report vomiting, diarrhea, appetite loss, weakness, collapse, or sudden lethargy, because these signs may indicate complications or overtreatment and need veterinary attention. The cortisol levels getting too low from the medication can induce a condition called Addison’s disease.
Living With a Pet That Has Cushing’s Disease
Many dogs with Cushing’s disease can enjoy a good quality of life when the condition is recognized, treated appropriately, and monitored carefully. Cats can be more medically complex, especially when diabetes and fragile skin are also present, but thoughtful case management can still improve comfort and daily function. The most helpful step for pet owners is early veterinary evaluation when a pet develops persistent increased thirst, increased urination, appetite changes, panting, abdominal enlargement, or unexplained skin changes.
When to Call Your Veterinarian Right Away
Contact a veterinarian promptly if a pet with suspected or diagnosed Cushing’s disease develops sudden weakness, collapse, severe vomiting or diarrhea, stops eating, has labored breathing, or develops skin tears or wounds. Cats with fragile skin should be handled gently and seen quickly if any tearing or self-trauma occurs. Early attention can help prevent complications and allows treatment plans to be adjusted before the pet becomes seriously ill.