Yes, cats can get Cushing's disease, though it is one of the rarest endocrine diagnoses in veterinary medicine—confirmed in well under 0.1% of cats presented to referral practices, with only a few hundred cases documented in the literature since the 1980s. Feline hyperadrenocorticism is almost always caused by a pituitary tumor driving excess cortisol production, and roughly 80% of confirmed cases occur in cats older than 10 years. The critical twist: about 80% of affected cats are also diabetic at diagnosis, and their diabetes is often profoundly insulin-resistant. In practical terms, Cushing's in cats is less a disease of "too much cortisol" in isolation and more a disease of stubborn, high-dose insulin requirements that refuse to stabilize.
The Mechanism: Why Feline Cushing's Looks Different
Cushing's disease—hyperadrenocorticism—means the adrenal glands secrete cortisol chronically and inappropriately. In roughly 80-85% of feline cases, the cause sits in the pituitary gland: a small adenoma overproduces ACTH, which orders the adrenal cortex to pump out cortisol. The remaining 15-20% are adrenal-dependent, caused by a cortisol-secreting adrenal tumor—a far higher adrenal-tumor share than in dogs, where only about 15% of cases are adrenal-dependent.
The feline difference runs deeper than prevalence. Cats are dramatically less sensitive to cortisol's suppressive effects on the immune system and skin. Where a Cushingoid dog develops a pot-bellied, hairless trunk within months, a cat can carry the same cortisol excess for years with only subtle signs. This tissue-level resistance explains why feline Cushing's is chronically underdiagnosed and why the classic canine "look" barely exists in cats.
In plain terms: the same hormone excess that wrecks a dog's body is partly "ignored" by a cat's body—so the first obvious clue is often a blood sugar that won't come down, not a changed appearance.
There is also a feedback-collapse detail worth understanding. Chronically high cortisol should suppress ACTH. But in pituitary-dependent disease, the adenoma ignores that feedback, and the normal pituitary tissue atrophies around it. This is why dexamethasone suppression tests—the backbone of canine diagnosis—frequently fail to suppress in cats at any dose, and why feline diagnosis leans on the combination of a low-dose dexamethasone suppression test plus endogenous ACTH measurement rather than either alone.
Quantified Context: How Rare, How Old, How Sick
The numbers matter because they shape clinical suspicion. Feline hyperadrenocorticism is estimated at fewer than 1 in 1,000 cats in general practice; even among diabetic cats—the highest-risk pool—prevalence estimates in referral populations run around 1-2%, with some screening studies reporting up to 5% of poorly controlled diabetics. Compare that to canine Cushing's, which affects an estimated 0.2-0.3% of all dogs and up to 20-25% of dogs over 12 years in some practice surveys—roughly a 50- to 100-fold diagnostic gap.
| Feature | Feline Cushing's | Canine Cushing's |
|---|---|---|
| Typical prevalence | Under 0.1% of cats | 0.2-0.3% of dogs |
| Adrenal-tumor share | 15-20% | About 15% |
| Concurrent diabetes | About 80% | About 10% |
| Median age at diagnosis | 10-12 years | 9-11 years |
| Classic skin thinning | Rare | Common |
| First-line medical therapy | Trilostane | Trilostane |
Age skew is pronounced: roughly 80% of feline cases are diagnosed after age 10, and fewer than 5% before age 7. Sex distribution is close to even, unlike the female predisposition seen in dogs. These demographics mean a young cat with insulin resistance almost never has Cushing's, while an older diabetic cat needing more than 1 unit per kilogram per injection deserves a workup.
The Diabetes Overlap: The Counterintuitive Core
The single most non-obvious fact about feline Cushing's is that the disease usually announces itself as treatment-resistant diabetes, not as an endocrine curiosity. Cortisol directly antagonizes insulin at the tissue level—it drives hepatic glucose output up and peripheral glucose uptake down. In a cat whose pancreas is already failing, that extra push tips the animal into insulin requirements of 2 to 10 units per kilogram per dose, versus a typical 0.5 to 1 unit per kilogram in uncomplicated feline diabetes.
This creates a diagnostic trap. A cat on 8 units twice daily with persistent blood glucose above 300 milligrams per deciliter looks like "bad diabetes management"—but the underlying driver may be a pituitary tumor. Vets who simply escalate insulin without investigating the resistance pattern can spend a year chasing numbers while the true cause goes untreated. Conversely, treating the Cushing's often drops insulin needs sharply within 2 to 8 weeks, sometimes by 50% or more, which means insulin doses must be reduced proactively to avoid hypoglycemia.
Timeline: From First Signs to Stabilization
The time course of feline Cushing's is slow and easily mistaken for normal aging, which is part of why diagnosis lags.
| Stage | Typical timeframe | What is happening |
|---|---|---|
| Subtle onset | 6-18 months before diagnosis | Increased thirst and urination blamed on age |
| Diabetes emerges | Often within 12 months of onset | Insulin resistance develops; doses climb |
| Insulin dose exceeds 2 units/kg | Weeks to months after diabetes onset | Red flag for endocrine workup |
| Diagnostic testing | 1-3 weeks | Low-dose dexamethasone suppression plus endogenous ACTH |
| Treatment started | Day of diagnosis | Trilostane titrated every 10-14 days |
| First recheck | 10-14 days | ACTH stimulation test to set dose |
| Stabilization | 1-3 months | Insulin needs fall; glucose curves flatten |
| Long-term monitoring | Every 3-6 months | Cortisol control plus diabetes review |
The 10-14 day recheck interval is not arbitrary. Trilostane's effect on cortisol can shift quickly in cats, and the manufacturer's monitoring protocol—an ACTH stimulation test 4-6 hours post-dose—exists to catch over-suppression before it causes adrenal crisis. Cats tolerate trilostane differently from dogs, and some require twice-daily dosing (dogs are often once-daily) to achieve stable control.
Diagnosis and Treatment Options: A Practical Comparison
Diagnosis is genuinely harder in cats than dogs. The low-dose dexamethasone suppression test (0.1 milligrams per kilogram) will suppress cortisol in most healthy cats at 8 hours; failure to suppress below 1.4 micrograms per deciliter supports Cushing's. Endogenous ACTH helps sort pituitary from adrenal origin: high-normal or elevated ACTH points to pituitary, suppressed ACTH to an adrenal tumor. Abdominal ultrasound looks for an adrenal mass, and pituitary imaging (CT or MRI) is reserved for surgical candidates.
| Option | Best suited for | Pros | Cons |
|---|---|---|---|
| Trilostane | Most cats, either form | Oral, titratable, well studied | Requires repeated ACTH stim tests; twice-daily dosing often needed |
| Mitotane | Pituitary-dependent cases | Can destroy adrenal cortex | Narrow margin, risk of adrenal crisis, limited feline data |
| Adrenalectomy | Adrenal tumors | Potential cure | Major surgery, 15-20% of cases only, perioperative risk |
| Hypophysectomy | Pituitary adenoma | Potential cure | Specialist-only, high cost, not widely available |
Adrenalectomy offers genuine cure for the 15-20% with adrenal tumors, with reported long-term remission in roughly 70-80% of surgical cases. Hypophysectomy—removal of the pituitary—can cure pituitary-dependent disease but is limited to a handful of referral centers and carries substantial perioperative mortality. For most owners, trilostane is the realistic path, and it is palliative rather than curative.
Misconceptions and Red Flags
A widespread misconception is that Cushing's is a dog disease that rarely touches cats, so feline cases are dismissed. Another is that a cat with a "pot belly" must have Cushing's; in cats, abdominal enlargement more often reflects obesity or fluid, and true Cushingoid body changes are uncommon. A third: that a normal dexamethasone suppression test rules Cushing's out—false, because stress and concurrent illness can cause false positives and the test can miss mild cases, so the endogenous ACTH result is essential.
Seek urgent veterinary care if a diabetic cat shows any of these:
- Blood glucose persistently above 400 milligrams per deciliter despite insulin doses above 2 units per kilogram per injection
- Sudden weakness, collapse, or seizure suggesting hypoglycemia after an insulin dose change
- Marked increase in thirst and urination developing over days, not weeks
- Poor wound healing or recurrent skin infections alongside diabetes
- Enlarged abdomen with muscle wasting, especially in a cat over 10 years old
The hypoglycemia bullet is the most safety-critical: once Cushing's is treated and insulin resistance falls, insulin doses that were previously correct can become dangerous within weeks.
What to Actually Do
If you suspect feline Cushing's, start by documenting the pattern rather than the snapshot. Keep a log of insulin doses, blood glucose readings taken at home if possible, water intake, and body weight over at least two weeks. Bring that log to the vet; the trend is often more diagnostic than any single test.
Ask directly whether the insulin resistance pattern warrants an endocrine workup, and specifically request the low-dose dexamethasone suppression test plus endogenous ACTH—not one alone. If an adrenal mass is found on ultrasound, ask about referral for surgical evaluation, because adrenalectomy is the only routine cure.
For cats already on trilostane, never adjust the dose without an ACTH stimulation test, and never raise insulin precipitously without rechecking cortisol control. Have a written plan for what to do if blood glucose drops below 100 milligrams per deciliter—typically a small meal of high-protein food and an immediate call to the vet.
Limitations: What the Evidence Still Cannot Say
Honesty about the evidence matters here. Feline Cushing's rests on small case series, not large randomized trials; the total published feline population is in the low hundreds, so most prevalence figures carry wide confidence intervals. Trilostane dosing protocols are extrapolated largely from canine data, and optimal feline starting doses and monitoring intervals are still debated. Whether early treatment of subtle, diabetes-free Cushing's in cats improves outcomes is essentially unknown.
There is also a genuine gray zone between "Cushing's" and "stress hypercortisolemia" in sick cats, and borderline test results should be interpreted with the whole clinical picture, not in isolation. The mechanism is well understood; the fine-grained management thresholds are not. That gap is exactly why feline Cushing's remains a diagnosis of pattern recognition and specialist collaboration rather than a single clean test.