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DISEASE · CATS

Cushing’s in cats: diabetes, fragile skin and the tests that confirm it

Cushing’s disease (hyperadrenocorticism) means the body makes too much cortisol. It is rare in cats and looks different from the disease in dogs. Most affected cats are diabetic, and their diabetes is hard to control. Some have skin so thin that it tears.

Written by the AI DiagAnimals editorial teamReviewed by the AI DiagAnimals TeamUpdated Our editorial policy

The essentials

Cushing’s disease is rare in cats and mostly affects older cats. In the largest case series, 90% of cats had poorly controlled diabetes and all had skin changes, often thin skin that tears. Unlike in dogs, a high ALP is uncommon, because cats have no cortisol-induced form of this enzyme. The low-dose dexamethasone suppression test is the preferred screening test in cats; the ACTH stimulation test misses many cases. Acromegaly, another hormone disease, is a more frequent cause of hard-to-control diabetes and is checked with IGF-1.

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What Cushing’s disease is in cats

The adrenal glands, near the kidneys, make cortisol. In Cushing’s disease they make too much of it. Spontaneous Cushing’s disease is rare in cats [1]. It mostly affects older cats, with a mean age at diagnosis of 10 years, and no purebred breed is predisposed [2].

In most cats a small tumor of the pituitary gland, at the base of the brain, drives the adrenal glands (pituitary-dependent disease): 27 of 30 cats in the largest series. In the other 3, a tumor of one adrenal gland was the cause [1]. Rarer adrenal tumors that make sex hormones can cause the same signs, and they are more common in cats than in dogs [2].

The signs owners notice

SignHow oftenTo know
Poorly controlled diabetes27 of 30 cats (90%) [1]The most common reason for referral; often resistant to insulin [1, 2].
Skin changes30 of 30 cats [1]Thin skin (70%), hair loss (60%), skin tears (57%) [1].
Drinking and urinating more87% [1]Also a sign of diabetes itself.
Pot belly, muscle loss67% each [1]A potbellied look is also seen in dogs with Cushing’s [11].
Increased appetite70% [1]Weight loss was noted in 47% of cats, weight gain in 23% [1].
Infections53% [1]Skin, urinary, respiratory or digestive, because cortisol weakens defenses [1, 2].

Up to a third of cats have skin so fragile that it can tear during handling, clipping or injections [2]. Thin skin and wounds that do not heal should make the vet think of Cushing’s disease [9].

What the blood work and urine show

  • Glucose: high in most cats, because most are diabetic and resist insulin [1, 2]. See diabetes in cats and blood sugar in cats.
  • ALP: raised in only 6 of 29 cats (21%), and ALT in 8 of 28 (29%), mostly when pancreatitis or liver disease was also present [1]. Dogs make a form of ALP induced by cortisol; cats do not, and feline ALP has a half-life of only about 6 hours in the blood [7]. See high liver enzymes in cats.
  • Cholesterol and triglycerides: cholesterol was abnormal in 9 of 24 cats (38%) and triglycerides were high in 5 of 7 (71%) [1].
  • Blood count: anemia in 13 of 27 cats (48%) [1]. See anemia in cats.
  • Thyroid: total T4 was normal in 84% of cats, unlike dogs with Cushing’s, where it is often low [1].
  • Urine: protein on the dipstick in 15 of 20 cats; bacteria grew in 3 of 15 urine cultures [1]. See urinalysis.

None of these changes is specific: the blood work raises the suspicion, and hormone tests confirm it [1].

How to read the glucose line

Here is an example line from a diabetic cat whose sugar stays high despite insulin.

An annotated line from a lab report · Illustrative example
AbbreviationResultUnitLaboratory intervalFlag
GLU Glucose412mg/dL60–120H
  1. Abbreviation GLU or GLUC: blood sugar.
  2. Result 412 mg/dL in this illustrative line: well above the interval.
  3. Unit mg/dL in the United States; mmol/L elsewhere (mg/dL ÷ 18). Use the converter below.
  4. Laboratory interval The example uses the cat interval of the Merck Veterinary Manual [10]; each laboratory sets its own.
  5. Flag H: above the interval. In a diabetic cat already on insulin, a sugar that stays high leads the vet to look for a cause of insulin resistance, such as acromegaly or Cushing’s disease [2, 12].

Unit converter

Equivalent values

  • Glucose, mmol/L–
  • Glucose, g/L–

Conversion only changes the unit. Compare the result with the interval printed by the laboratory that measured it.

How Cushing’s is diagnosed in cats

  • Low-dose dexamethasone suppression test: blood cortisol is measured before and 4 and 8 hours after an injection of dexamethasone, a cortisone-like drug. In a healthy cat cortisol falls; in Cushing’s it does not. Results fitted Cushing’s in 27 of 28 cats (96%), and it is the recommended first test [1]. Cats need a higher dose than dogs for this test [2].
  • ACTH stimulation test: less useful in cats. It was positive in only 9 of 16 affected cats (56%) and normal in all 3 cats with an adrenal tumor [1]. See the ACTH stimulation test in dogs.
  • Urine cortisol:creatinine ratio: measured on a urine sample. The ratio was higher in cats with pituitary-dependent Cushing’s than in healthy cats [6], but sick cats also have higher ratios than healthy ones (median 14.8 versus 3.2) [5], so a high result is not specific.
  • Abdominal ultrasound: the look of the adrenal glands (both enlarged, or one enlarged) matched the final type of disease in 28 of 30 cats (93%) [1].
  • Endogenous ACTH: was consistent with pituitary disease in 7 of 8 cats tested, but the sample needs special handling and most assays have not been validated in cats [1].
  • CT or MRI of the head: showed a pituitary tumor in all 9 cats imaged [1].

Cushing’s or acromegaly?

Most diabetic cats have an ordinary form of diabetes, but a significant share have diabetes caused by another hormone disease [12]. The main one is acromegaly (hypersomatotropism), an excess of growth hormone from a pituitary tumor. In 1,221 diabetic cats screened in the UK, about a quarter (24.8%) were estimated to have it [3]. It is screened with a blood test for IGF-1: a value above 1,000 ng/mL had a positive predictive value of 95% [3]. Most of these cats did not look acromegalic [3].

Both diseases can make diabetes hard to control [12]. Thin, fragile skin is a typical sign of Cushing’s disease [1, 11].

Outlook

Studies are small. In 15 cats given medical treatment that lowers cortisol production, signs improved in 13, insulin needs fell in 6 of 9 diabetic cats, and median survival was 617 days [4]. In an older series of 10 cats that had adrenal surgery, 3 died within 5 weeks of complications; in the other 7, signs resolved within 2 to 4 months and 4 of 6 diabetic cats no longer needed insulin [8]. Surgery on the adrenal glands or the pituitary gland is the only curative option; radiation or medicines may improve signs [2]. Skin fragility can weigh heavily on quality of life [9].

Related articles

En français : la maladie de Cushing du chat.

Questions to ask your veterinarian

  1. Could a hormone disease explain why my cat’s diabetes is hard to control?
  2. Should we test IGF-1 for acromegaly, or do a dexamethasone suppression test?
  3. Is the ALP normal, and does that change anything in a cat?
  4. What does the ultrasound show about the adrenal glands?
  5. How can we handle my cat’s skin safely during tests?
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Frequently asked questions

What are the signs of Cushing’s in cats?

Poorly controlled diabetes, thin skin that can tear, hair loss, a pot belly, muscle loss, increased thirst, urination and appetite, and repeated infections [1, 2].

How is Cushing’s diagnosed in cats?

With a low-dose dexamethasone suppression test, the preferred test in cats, then an abdominal ultrasound to see the adrenal glands. The ACTH stimulation test misses many cases [1].

Is Cushing’s in cats linked to diabetes?

Yes. Most cats with Cushing’s are diabetic, and their diabetes is often resistant to insulin: 90% in the largest series [1, 2].

Is Cushing’s disease common in cats?

No. It is rare, and much less common than in dogs [1]. Acromegaly is a more frequent hormonal cause of hard-to-control diabetes [3].

Do cats with Cushing’s have a high ALP?

Usually not: ALP was raised in only 21% of cats in one series. Cats do not make the cortisol-induced ALP seen in dogs [1, 7].

Sources

  1. Valentin SY et al. Clinical findings, diagnostic test results, and treatment outcome in cats with spontaneous hyperadrenocorticism: 30 cases. J Vet Intern Med. 2014;28(2):481-487. doi.org/10.1111/jvim.12298
  2. Boland LA, Barrs VR. Peculiarities of feline hyperadrenocorticism: update on diagnosis and treatment. J Feline Med Surg. 2017;19(9):933-947. doi.org/10.1177/1098612X17723245
  3. Niessen SJ et al. Studying cat (Felis catus) diabetes: beware of the acromegalic imposter. PLoS One. 2015;10(5):e0127794. doi.org/10.1371/journal.pone.0127794
  4. Mellett Keith AM et al. Trilostane therapy for treatment of spontaneous hyperadrenocorticism in cats: 15 cases (2004-2012). J Vet Intern Med. 2013;27(6):1471-1477. doi.org/10.1111/jvim.12178
  5. Henry CJ et al. Urine cortisol:creatinine ratio in healthy and sick cats. J Vet Intern Med. 1996;10(3):123-126. doi.org/10.1111/j.1939-1676.1996.tb02043.x
  6. Goossens MM et al. Urinary excretion of glucocorticoids in the diagnosis of hyperadrenocorticism in cats. Domest Anim Endocrinol. 1995;12(4):355-362. doi.org/10.1016/0739-7240(95)00046-h
  7. eClinPath, Cornell University College of Veterinary Medicine. Alkaline phosphatase. eclinpath.com/chemistry/liver/cholestasis/alkaline-phosphatase
  8. Duesberg CA et al. Adrenalectomy for treatment of hyperadrenocorticism in cats: 10 cases (1988-1992). J Am Vet Med Assoc. 1995;207(8):1066-1070. pubmed.ncbi.nlm.nih.gov/7559048
  9. Hardy L et al. Skin fragility in a cat presenting with pituitary-dependent hyperadrenocorticism. JFMS Open Rep. 2023;9(1):20551169231171245. doi.org/10.1177/20551169231171245
  10. Merck Veterinary Manual. Serum biochemical analysis reference ranges. merckvetmanual.com/reference-values-and-conversion-tables/reference-guides/serum-biochemical-analysis-reference-ranges
  11. Chiaramonte D, Greco DS. Feline adrenal disorders. Clin Tech Small Anim Pract. 2007;22(1):26-31. doi.org/10.1053/j.ctsap.2007.02.004
  12. Niessen SJ et al. Hypersomatotropism, acromegaly, and hyperadrenocorticism and feline diabetes mellitus. Vet Clin North Am Small Anim Pract. 2013;43(2):319-350. doi.org/10.1016/j.cvsm.2012.12.004

Laboratory methods and reference intervals vary. This article explains; it does not diagnose. For a decision about your pet, use the original report and talk to your veterinarian. Our editorial policy.

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