What actually happens in a cat's body with Cushing's disease?

Hyperadrenocorticism develops when the adrenal glands, two small structures sitting just cranial to each kidney, pump out chronically excessive amounts of cortisol. Cortisol is a normal stress hormone that helps regulate metabolism, blood sugar, and inflammation, but sustained overproduction damages skin, muscle, and blood vessels over time. The Merck Veterinary Manual classifies feline hyperadrenocorticism as an uncommon disease, occurring far less often than in dogs, and notes that roughly 80% of affected cats have a pituitary tumor driving the excess cortisol output while the remainder have a primary adrenal tumor (Merck Veterinary Manual, 2023). Because cats' adrenal glands are comparatively resistant to the tissue damage steroids cause in dogs, cases tend to go unnoticed longer before the classic physical changes appear.

A second, distinct pathway to the same hormone problem is iatrogenic: long-term corticosteroid drugs like prednisolone, given to control asthma, allergic skin disease, or inflammatory bowel disease, can suppress a cat's own adrenal function and occasionally trigger Cushing's-like signs. Cornell Feline Health Center material on feline endocrine disease notes that most naturally occurring feline Cushing's cases are diagnosed in middle-aged to older cats, typically between 8 and 14 years old, and that the disease is reported far less frequently in the veterinary literature than canine Cushing's, with only a few hundred confirmed cases described worldwide (Cornell Feline Health Center, 2021).

What are the first signs an owner is likely to notice at home?

Excessive thirst and urination are almost always the earliest complaints, since cortisol interferes with the kidneys' ability to concentrate urine and the cat compensates by drinking more. Owners frequently describe a cat draining a water bowl that used to last all day, or crying at the bathroom faucet. The Merck Veterinary Manual lists polyuria, polydipsia, and a ravenous appetite as the most consistent early findings, alongside a pot-bellied abdominal enlargement that develops as abdominal muscles weaken and the liver enlarges (Merck Veterinary Manual, 2023).

Skin changes tend to show up later but are the most alarming: the skin becomes thin, fragile, and easily torn, sometimes splitting open during routine handling, grooming, or even normal play, a condition veterinary dermatologists call feline skin fragility syndrome. Hair loss, poor coat quality, and curling of the ear tips are also reported findings. Because more than 80% of cats with hyperadrenocorticism also have concurrent diabetes mellitus that is difficult to regulate with insulin, unexplained insulin resistance in a diabetic cat is itself a red flag that should prompt Cushing's testing (American College of Veterinary Internal Medicine, 2020).

What causes Cushing's disease in cats, and which cats are at risk?

The overwhelming majority of naturally occurring cases stem from a functional tumor of the pituitary gland, usually a benign adenoma, that continuously signals the adrenal glands to release cortisol regardless of the body's actual needs. A smaller subset arises from a tumor directly in one adrenal gland, which can be benign or malignant. There is no confirmed breed predisposition, but the disease is consistently reported in middle-aged and senior cats, and diabetic cats appear to be overrepresented among diagnosed cases because insulin resistance prompts vets to look harder for an underlying endocrine driver (Merck Veterinary Manual, 2023).

A separate, iatrogenic form results from prolonged use of injectable or oral corticosteroids prescribed for chronic allergic or respiratory disease. Cats tolerate steroids better than dogs at a tissue level, so this route to hyperadrenocorticism is considered rare, but veterinarians still weigh cumulative steroid dose and duration when a cat on long-term therapy develops new drinking, urination, or skin changes (Merck Veterinary Manual, 2023).

How do veterinarians actually diagnose Cushing's disease in a cat?

Diagnosis starts with baseline bloodwork and urinalysis, which commonly show elevated glucose, glucosuria, and sometimes elevated liver enzymes, but no single blood value confirms hyperadrenocorticism. Vets then turn to hormone-specific screening tests, most often a low-dose dexamethasone suppression test or a urine cortisol-to-creatinine ratio, to demonstrate that cortisol production is not being appropriately regulated (American College of Veterinary Internal Medicine, 2020). Because these screening tests can produce false positives in sick or stressed cats, results are always interpreted alongside the cat's clinical picture rather than in isolation.

Once hyperadrenocorticism is confirmed, abdominal ultrasound or CT imaging is used to determine whether the problem originates in the pituitary gland or in one of the adrenal glands, since the two forms are treated differently. An enlarged adrenal gland on ultrasound suggests a primary adrenal tumor, while symmetrically normal-sized or enlarged adrenal glands point toward pituitary-dependent disease. Advanced imaging such as MRI of the pituitary gland may be recommended at a referral hospital when surgery or radiation therapy is being considered (Merck Veterinary Manual, 2023).

What are the treatment options once a cat is diagnosed?

Medical management with trilostane, a drug that blocks cortisol synthesis in the adrenal gland, is the most commonly used treatment and requires careful dose titration with repeat hormone testing, typically starting with rechecks 10 to 14 days after starting or adjusting the dose (American College of Veterinary Internal Medicine, 2020). Trilostane is not FDA-approved for cats specifically, so its use is considered extra-label and is managed under close veterinary supervision with monitoring for signs of underdosing or overdosing, including lethargy, vomiting, or worsening diabetes control.

Surgical removal of the affected adrenal gland is an option when imaging identifies a discrete adrenal tumor, and can be curative, though adrenalectomy carries meaningful surgical risk given the gland's location near major blood vessels and the fragile condition of the skin and tissues in affected cats. For pituitary-dependent disease, radiation therapy targeting the pituitary tumor is used at some specialty and university referral centers, though access is limited and cost is substantial. Whichever the underlying cause, concurrent diabetes almost always requires simultaneous, carefully adjusted insulin therapy, since cortisol excess directly antagonizes insulin's effects (Merck Veterinary Manual, 2023).

How do you manage a Cushing's cat day to day at home?

Home care centers on protecting fragile skin and staying consistent with medication and monitoring schedules. Owners are advised to handle affected cats gently, avoid rough play or restraint that could tear skin, keep nails trimmed to reduce accidental scratches, and watch closely for any new wounds, since torn skin in these cats heals poorly and is prone to infection. Litter box hygiene and prompt attention to urinary changes matter too, since Cushing's cats are prone to recurrent urinary tract infections from dilute urine and impaired immune function (Merck Veterinary Manual, 2023).

Because most affected cats are also diabetic, home glucose monitoring — either with a handheld glucometer on ear or paw pad blood or a continuous glucose monitor applied to the skin — is frequently part of the daily routine, alongside a consistent feeding schedule timed to insulin injections. Owners should keep a symptom log tracking water intake, appetite, and any new skin lesions to bring to recheck appointments, since trends over days matter more than any single observation when adjusting trilostane or insulin doses (American College of Veterinary Internal Medicine, 2020).

What's the long-term outlook for a cat with Cushing's disease?

Prognosis is guarded and depends heavily on how well concurrent diabetes can be controlled and how fragile the skin has become by the time of diagnosis. Cats managed medically with trilostane and stable insulin dosing can survive from several months to a couple of years, though published case series remain small given how uncommon the disease is, and outcomes vary widely case to case (Merck Veterinary Manual, 2023). Cats undergoing successful adrenal tumor removal without significant surgical complications have the best chance at meaningful remission, since the source of excess cortisol is physically eliminated.

Regardless of treatment path, lifelong monitoring is the rule rather than the exception: repeat hormone testing, blood glucose curves, and physical skin checks are typically scheduled every few weeks initially and then spaced out as the cat stabilizes. Because the disease is rare enough that many general practice vets diagnose only a handful of cases in a career, referral to or consultation with a veterinary internal medicine specialist is commonly recommended to guide both diagnosis and long-term dose adjustments (American College of Veterinary Internal Medicine, 2020).