Feline acromegaly is a pituitary tumor that pumps out growth hormone, and the most common way it shows up at home is a previously controlled diabetic cat who suddenly needs huge insulin doses and still drinks and pees constantly. Roughly 1 in 4 diabetic cats has underlying acromegaly when systematically screened, far more than vets recognized 15 years ago (Niessen et al., 2015, JVIM). Recognizing the pattern early — escalating insulin needs, big paws and a broad jaw, gradual weight gain despite uncontrolled diabetes — lets you confirm with IGF-1 and refer for radiation therapy before heart and kidney complications take hold.
Last reviewed: June 2026
What Acromegaly Actually Is
Acromegaly in cats is a slow-growing benign pituitary tumor that secretes excess growth hormone (GH). GH drives insulin resistance, organ enlargement, and a recognizable change in facial and paw conformation. The condition is also called hypersomatotropism. The bulk of affected cats are middle-aged to older neutered males, although females are absolutely seen. The UK ALIVE screening project tested 1,221 diabetic cats and found IGF-1 elevations consistent with acromegaly in 24.8 percent — meaning roughly 1 in 4 diabetic cats has this disease, almost all undiagnosed at the time of testing (Niessen et al., 2015, JVIM). The clinical implication is direct: any insulin-resistant diabetic cat deserves IGF-1 screening, not just the ones with obvious facial changes.
The Insulin-Resistance Pattern That Tips Vets Off
The single biggest red flag is a diabetic cat whose insulin dose keeps climbing without ever achieving good control. A typical newly diagnosed diabetic cat is regulated on 1 to 3 units of insulin twice daily. An acromegalic cat often needs 6, 10, or 20 units twice daily and still has high blood glucose, persistent polydipsia and polyuria, and a stubbornly elevated fructosamine. Owners frequently describe a cat who keeps eating ravenously, drinks bowl after bowl of water, and is gaining weight or holding weight despite the diabetes — the opposite of the classic weight-loss-in-uncontrolled-diabetes picture. The 2018 AAHA/AAFP feline diabetes guideline flags suspected acromegaly when insulin requirements exceed roughly 1.5 units per kilogram per dose, or higher with confirmed good owner technique and storage (Behrend et al., 2018, JFMS (AAHA/AAFP Diabetes Guidelines)).
Physical Changes Owners Sometimes Notice
Because GH excess remodels soft tissue and bone, the cat's appearance slowly shifts. Paws look thicker and rounder, the lower jaw juts forward (prognathism), the face widens, the bridge of the nose looks broader, and gaps may open between the teeth as the jaw remodels. The voice may deepen and the cat may snore. Internally, the heart muscle thickens — about 70 to 90 percent of acromegalic cats have echocardiographic evidence of left ventricular hypertrophy, which can look identical to HCM on a screening echo. Kidney enlargement, organomegaly, and a swollen tongue are common at necropsy. Most owners only recognize these changes in retrospect after the diagnosis is made, because they happen over many months.
How Diagnosis Is Confirmed
Diagnosis rests on a high serum IGF-1 (insulin-like growth factor 1) in a diabetic cat that has been on insulin for at least 6 weeks. IGF-1 above approximately 1,000 ng/mL is highly suggestive in a diabetic cat; values above 1,500 ng/mL are essentially diagnostic in the right clinical setting. The reason for the insulin-stabilization wait is biological: untreated diabetic cats can have falsely low IGF-1, so testing too early misses cases. Once IGF-1 is elevated, the pituitary mass is confirmed and measured with contrast CT or MRI of the brain. As described in Ettinger's Textbook of Veterinary Internal Medicine, imaging is essential because tumor size guides treatment options and prognosis.
Treatment Options in 2026
Three treatment paths exist. Stereotactic radiation therapy is the most widely available curative option in the US, with 70 to 90 percent of cats achieving diabetic remission or marked reduction in insulin needs within 6 to 12 months post-treatment. Treatment is typically delivered as 1 to 3 fractions under anesthesia at a referral center. Hypophysectomy — surgical removal of the pituitary — is done at a small number of academic centers; reported remission rates exceed 90 percent but lifelong hormone replacement is required. Medical management with the somatostatin analog pasireotide is an emerging option in cats with documented IGF-1 response, though access remains limited. If owners decline definitive treatment, supportive care with very high insulin doses, careful diabetic monitoring, and treatment of secondary heart disease can maintain quality of life for months to years.
Why Early Recognition Matters
The longer acromegaly goes undiagnosed, the more secondary disease accumulates. Cats develop left ventricular hypertrophy, chronic kidney disease, and recurrent respiratory infections from soft-tissue thickening. Most importantly, uncontrolled diabetes for months drives glycemic neuropathy, weight loss late in the course, and the everyday burden of polydipsia and polyuria for the family. Catching acromegaly within 3 to 6 months of insulin starting — and referring before cardiac and renal disease are established — gives the best prognosis. The 2021 AAFP-AAHA Feline Life Stage Guidelines, 2021 recommend a structured workup for insulin-resistant feline diabetes that explicitly includes IGF-1 screening.
When to See a Vet
Call your vet today if:
- Your diabetic cat needs an insulin dose increase for the third or fourth time and is still drinking and urinating excessively
- Insulin requirement is above 1.5 units per kilogram per dose with documented good technique
- Your cat's face, jaw, or paws look noticeably broader than a year ago
- A previously stable diabetic cat starts gaining weight while glucose remains poorly controlled
- New onset of snoring, voice change, or a heart murmur in a middle-aged diabetic cat
Go to the ER immediately if:
- Open-mouth or labored breathing at rest (possible heart failure)
- Sudden hindlimb paralysis with cold paws (saddle clot)
- Vomiting, profound lethargy, and breath that smells like nail polish remover (diabetic ketoacidosis)
- Collapse, weakness, or pale gums
- A diabetic cat who is suddenly hypoglycemic and disoriented after a dose change
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Frequently Asked Questions
What is the first symptom of acromegaly in cats most owners notice?
In practice, the first noticeable change is rising insulin requirements in a previously stable diabetic cat. The cat keeps drinking and urinating, the blood glucose stays high, and the dose keeps creeping up. Physical changes like a wider face, larger paws, or a protruding jaw usually become obvious only in retrospect once IGF-1 confirms the diagnosis.
How much does diagnosis and treatment cost?
Initial vet exam is typically $50 to $150 in the US. A serum IGF-1 test runs $80 to $150 at most reference labs. Pituitary imaging with contrast MRI is $1,500 to $3,000 at a referral center. Stereotactic radiation therapy ranges from $6,000 to $12,000 depending on the institution and number of fractions. Long-term insulin and monitoring add $40 to $150 per month. Catching it early avoids years of expensive insulin escalation.
Is feline acromegaly the same as Cushing's disease in cats?
No. Cushing's disease (hyperadrenocorticism) is excess cortisol; acromegaly is excess growth hormone. Both cause insulin-resistant diabetes in cats, and the two can occur together, but they are different pituitary problems with different tests and different treatments. IGF-1 distinguishes acromegaly; a low-dose dexamethasone suppression test or urine cortisol:creatinine ratio works up Cushing's.
Can an acromegalic cat have diabetic remission?
Yes, particularly after stereotactic radiation or hypophysectomy. Studies of stereotactic radiation report 30 to 50 percent of cats achieving full diabetic remission and another 30 to 40 percent achieving large reductions in insulin requirements (Wormhoudt et al., 2018, JVIM). Hypophysectomy series report remission rates above 90 percent. Untreated, spontaneous remission is rare.
Do all diabetic cats need an IGF-1 test?
Most internal medicine specialists now recommend IGF-1 screening for any diabetic cat that has been on insulin at least 6 weeks, especially those with insulin requirements above 1.5 units per kilogram per dose, persistent polydipsia despite treatment, weight gain on insulin, or any of the physical features (broad face, big paws, prognathism). Screening earlier than 6 weeks risks a falsely low result.
What is the life expectancy of a cat with acromegaly?
Untreated cats with advanced disease often live 1 to 3 years from diagnosis, ultimately limited by heart failure or chronic kidney disease. Cats that receive stereotactic radiation have reported median survivals of 2 to 5 years, with many living a normal feline lifespan once the underlying disease is controlled and diabetes resolves or improves substantially.
Are certain breeds at higher risk?
Acromegaly is reported across breeds and is most common in middle-aged to older cats. Domestic shorthairs make up the bulk of cases simply because they are the most common cat. There is no well-established breed predisposition, although males are over-represented at roughly 2 to 1.
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