Excess growth hormone production is also called hypersomatotropism. Acromegaly specifically describes the associated tissue growth changes. These terms do not mean exactly the same thing: a cat can have the hormonal disorder without characteristic outward features. Not every patient develops diabetes either, and diabetes does not always have to be difficult to control.
When to see a vet urgently
Seek immediate care if your cat develops any of the following:
- sudden weakness, unsteadiness, seizures or reduced consciousness;
- difficulty breathing or rapidly worsening breathing noise;
- refusal to eat, vomiting and a clear decline in general health in a cat with diabetes;
- collapse or unusual behaviour that worsens quickly.
Symptoms in a cat receiving insulin may also involve blood sugar that is too low. Ask the veterinary practice for immediate instructions. You can find a vet near you.
Overview
In acromegaly, a pituitary tumour secretes too much growth hormone (GH), which also raises insulin-like growth factor 1 (IGF-1). This causes metabolic disturbances, structural changes and severe insulin resistance. Acromegaly is considered an under-recognised cause of diabetes that does not respond to treatment in cats.
Growth hormone interferes with insulin's action in both tissues and the liver. Cells take up glucose less effectively, and liver glucose production is not suppressed normally. Insulin resistance means this reduced response to insulin. Simply increasing insulin does not remove the source of excess hormone production.
IGF-1 forms mainly in the liver under the influence of growth hormone and contributes to tissue growth. Its blood level remains steadier than growth hormone, making it useful in practical testing. A tumour's hormonal effect and pressure caused by its size are different problems: even a small lesion can have an important hormonal effect.
Causes
- a hormonally active pituitary adenoma, the main cause;
- less commonly, overgrowth of growth hormone-producing pituitary cells;
- inherited predisposition has not been demonstrated, but the disease usually develops in older cats.
Risk factors
- older cats, over 8–10 years old;
- males, which are affected more often than females;
- cats with difficult-to-control diabetes;
- cats with chronic hormonal disorders.
Difficult-to-control diabetes is a reason to suspect an underlying disease, but does not itself cause a pituitary tumour. Chronic hormonal disorders do not form a single, clearly established tumour risk group either. Age and sex are observations associated with susceptibility, rather than diagnostic criteria. The disease is not ruled out in a female or younger cat.
Typical symptoms
- signs of difficult-to-control diabetes: increased urination, thirst, excessive eating and weight loss despite treatment;
- thickening of the skull and enlarged jaws;
- soft tissue growth, including broad paws and thickened skin;
- a hoarser voice;
- snoring and difficulty breathing;
- enlarged internal organs, including the heart and liver;
- neurological symptoms as the tumour grows, including apathy, behaviour changes and seizures.
Obvious enlargement of the face or paws may be absent, so do not wait for appearance changes before seeking investigation. Weight gain despite poor diabetes control can also raise suspicion. In this situation, weight change is not always explained by body fat; tissue growth may contribute too.
Snoring or harsh breathing sounds may involve soft tissues around the throat and tongue. Heart changes or movement difficulties can develop at the same time. These also have other causes, so each new symptom is assessed separately. Older photographs and your observations of when changes occurred can help build the history.
Complications and consequences
- difficult-to-control diabetes requiring large insulin doses;
- hypertrophic cardiomyopathy;
- respiratory failure due to soft tissue thickening;
- neurological disturbances as the tumour presses on the brain;
- death without treatment.
The course of untreated disease varies, and not every complication develops in every cat. Diabetes control, airway and heart health, and any pressure effects of the tumour are assessed as separate treatment needs. Serious neurological symptoms may need urgent assessment regardless of blood glucose measured at home.
Diagnosis at the vet
- clinical signs in a cat whose diabetes does not respond to treatment;
- blood IGF-1 measurement, with an elevated result being an important marker;
- brain MRI or CT to image a pituitary tumour;
- blood biochemistry to assess liver and kidney function;
- heart ultrasound to identify cardiomyopathy.
More common reasons for poor diabetes control are also checked first. Insulin storage, the injection device and administration technique are reviewed. Your vet also looks for dental or other infections, pancreatic disease and medicines that can increase insulin resistance, for example. Not every increase in insulin requirement therefore results from hypersomatotropism.
The IGF-1 result is interpreted alongside the medical history. In newly diagnosed diabetes with insulin deficiency, it may be lower than expected because normal liver IGF-1 production requires insulin's action. An unclear or borderline result can be retested as treatment progresses. One low result early on does not always rule out the disease.
MRI or CT helps assess pituitary size, tumour location and planning for a possible procedure. A small tumour or cell overgrowth is not always visible. Normal imaging alone therefore does not overturn strong hormonal suspicion. Images, IGF-1 results and the overall clinical picture are compared.
Heart ultrasound and other organ-specific investigations are selected according to findings. They assess both concurrent complications and treatment safety. Tumour size or IGF-1 alone does not establish how much insulin your cat needs or their quality of life.
Treatment
- radiotherapy for the pituitary tumour, which reduces its size; many cats need less insulin and some achieve diabetic remission;
- removal of the pituitary gland, or hypophysectomy, the most effective method, but performed at only a few specialist centres; lifelong hormone replacement is needed afterwards;
- medical treatment with pasireotide, a somatostatin analogue with limited availability;
- if the tumour is not treated, diabetes is managed with large insulin doses under veterinary supervision, and the outlook is guarded.
Tumour-directed treatment and diabetes management are planned together. Surgery can lead to a substantial fall in hormone levels and diabetic remission, but the result cannot be promised in advance. Patient selection, other illnesses and the ability to provide aftercare affect suitability. Good results from small surgical series are not interpreted as every cat's chance of success.
After hypophysectomy, replacement is also needed for hormones whose normal production depended on the removed pituitary gland. Successful treatment requires you to be able to provide home care and monitoring. Possible recovery problems, such as changes in drinking or eye symptoms, are assessed according to the practice's instructions.
Radiotherapy's effects on the tumour and diabetes can be delayed. It may help neurological symptoms caused by pressure even if hormone levels do not fully normalise. Pasireotide can reduce insulin requirements, but does not automatically shrink the tumour. Response and possible gastrointestinal adverse effects are monitored individually.
Even when tumour-directed treatment is not possible, care can support diabetes control and your cat's comfort. Goals include adequate nutrition, controlling thirst and urination, and avoiding excessively low blood sugar. Do not increase insulin doses yourself solely because of thirst, one reading or a high IGF-1 value.
Home care and monitoring treatment response
Insulin requirements can fall rapidly after tumour treatment. The risk of low blood sugar needs careful attention, and postoperative hypoglycaemia has been described even after injected insulin has been stopped. Monitoring and medication changes are therefore planned by the care team. Report symptoms promptly even after apparently successful treatment.
Record appetite, drinking, weight, urination and medicines given. Home blood glucose monitoring or an interstitial glucose sensor can help if part of the agreed plan. Results are considered alongside health: an unusually low sensor reading may need checking, and seeking care for a symptomatic cat must not be delayed because a measurement is uncertain.
If your cat will not eat, vomits or cannot receive medicines successfully, ask the practice for instructions the same day. Diabetic ketoacidosis, an acid build-up associated with insulin deficiency, can occur even in a cat receiving medication. Do not put food or fluid into the mouth of a cat that is having seizures or is unconscious.
The outlook depends on control of the hormonal disorder, the tumour's effects and existing organ changes. Diabetic remission does not mean that all earlier tissue changes have disappeared. Monitoring is needed even when insulin is no longer required. Choosing treatment also considers the practical feasibility of home care alongside your cat's condition.
Prevention
- There is no specific way to prevent acromegaly.
- Weight management and treatment of hormonal disorders can reduce metabolic strain.
- Diagnose diabetes early and see your vet promptly if insulin does not seem effective.
Important for cat owners
A growth hormone-secreting pituitary tumour is a rare but important cause of severe diabetes. Remember that if your cat's diabetes is difficult to control and insulin requirements keep increasing, investigation for acromegaly is worthwhile. Modern tests, including IGF-1 and MRI, help identify the disease and choose treatment, substantially improving the outlook and quality of life.
However, hypersomatotropism is not currently considered rare specifically among diabetic cats. Discussing testing may also be appropriate for a cat with relatively well-controlled diabetes. Prevalence estimates in the general cat population and among cats with diabetes are not the same thing.
This article provides general information and does not replace veterinary care. Contact your vet if you notice signs of illness in your cat.
Frequently asked questions
Can a cat have acromegaly without enlarged paws?
Yes. Excess growth hormone can occur without obvious outward growth changes. A diabetic cat that looks ordinary may therefore still need IGF-1 testing.
Does a low IGF-1 result rule out the disease?
Not always. Insulin deficiency and test timing can affect the result. Your vet assesses the need for repeat testing using symptoms, diabetes treatment response and other findings.
Can insulin be stopped after tumour treatment?
Some cats achieve diabetic remission, but this cannot be promised. Insulin requirements can change quickly, so doses are changed only according to monitoring and your vet's instructions.
This article is for general information only and is not a guide to treatment. If you notice the first signs of illness, contact your vet.
Paw4care editorial team
Sources
- Acromegaly in Cats, Merck Veterinary Manual, accessed 2026-11-05.
- Evaluation of hypophysectomy for treatment of hypersomatotropism in 25 cats, Journal of Veterinary Internal Medicine, accessed 2026-11-05.
- Growth Hormone and IGF-1 in Cats, Michigan State University Veterinary Diagnostic Laboratory, accessed 2026-11-05.
- iCatCare 2025 consensus guidelines on the diagnosis and management of diabetes mellitus in cats, Journal of Feline Medicine and Surgery / International Cat Care, accessed 2026-11-05.
- Troubleshooting in Diabetic Cats, American Animal Hospital Association, accessed 2026-11-05.
- Insulin Treatment and Monitoring, American Animal Hospital Association, accessed 2026-11-05.
- Feline Diabetes, Cornell Feline Health Centre, accessed 2026-11-05.
- Section 12: Diabetic Ketoacidosis in Cats, American Animal Hospital Association, accessed 2026-11-05.