A Condition Hidden Behind Difficult Diabetes
If your diabetic cat seems to need ever-increasing doses of insulin to achieve even modest blood glucose control, acromegaly should be on your veterinary team's radar. This hormonal condition, caused by a tumour in the pituitary gland that overproduces growth hormone, is considerably more common in diabetic cats than was once thought. Estimates suggest it may account for anywhere between a quarter and a third of cases of insulin-resistant feline diabetes.
Acromegaly tends to be diagnosed later than it should be, partly because its physical changes emerge gradually, and partly because insulin resistance in diabetic cats is attributed to other causes first. Understanding the condition helps owners advocate earlier for the right investigations.
What Is Acromegaly and What Causes It
Acromegaly means abnormal growth — specifically, an excess of growth hormone (GH) driving excessive tissue expansion in an adult animal. In cats, this nearly always stems from a functional pituitary adenoma: a benign but hormonally active tumour in the pituitary gland at the base of the brain. The excess GH also stimulates production of insulin-like growth factor 1 (IGF-1) in the liver, and it is actually IGF-1 that drives much of the physical change seen in affected cats.
Growth hormone directly antagonises the action of insulin. It pushes cells to use fat for energy instead of glucose, so blood sugar remains elevated regardless of how much insulin is administered. This is the mechanism behind acromegaly-driven insulin resistance, and it is profound — some affected cats require ten times or more the normal insulin dose without achieving good control.
Physical Changes Worth Noticing
Because acromegaly causes sustained excessive growth, affected cats often show characteristic physical changes over time. These develop slowly, sometimes over years, which is why owners may not recognise them as abnormal:
- Increased body size and weight, despite diabetes being present
- Broad, rounded facial features — the face may look subtly wider or coarser than before
- Enlarged paws and thickened skin
- Increased interdental spacing — gaps appearing between the teeth
- Abdominal enlargement due to organ growth (organomegaly)
- Increased snoring or upper airway noise due to soft tissue expansion
- A deep, husky voice in some cats
Weight gain in a diabetic cat is particularly telling. Diabetes typically causes weight loss because glucose cannot enter cells properly. A diabetic cat gaining weight despite poor glycaemic control is almost paradoxical — and acromegaly is one of the primary explanations.
How Vets Investigate Acromegaly
The first step is usually measuring serum IGF-1. Elevated IGF-1 in a diabetic cat with insulin resistance is a strong indicator of acromegaly, and the test is relatively accessible at most veterinary laboratories. It is not infallible — IGF-1 can be elevated in some cats without acromegaly, and stress can affect values — but it is a practical screening tool.
Definitive diagnosis requires advanced imaging. MRI of the brain is the gold standard, allowing direct visualisation of a pituitary tumour. CT scanning is a more accessible alternative at many specialist centres and can detect larger tumours effectively. Not all pituitary adenomas are large enough to be seen on imaging, particularly in the early stages, which means some cats are treated based on clinical and biochemical findings without a tumour being definitively confirmed.
Treating Acromegaly in Cats
There is no single universally available curative treatment, and management options vary considerably depending on what is accessible in your region.
Radiation Therapy
Stereotactic radiotherapy — high-precision radiation targeted at the pituitary tumour — is the most effective treatment currently available and has produced excellent outcomes in cats treated at specialist centres. Many cats experience significant improvement in glycaemic control, and some achieve diabetic remission after successful tumour irradiation. Access is limited to referral centres with appropriate equipment, and the cost is substantial.
Hypophysectomy
Surgical removal of the pituitary gland has been performed in cats with acromegaly at a small number of specialist centres, particularly in the Netherlands where the technique has been refined over many years. Outcomes in experienced hands are promising, with high rates of diabetic remission post-operatively. The procedure carries significant risks and requires intensive post-operative management, including lifelong hormone replacement therapy.
Medical Management
Pasireotide, a somatostatin analogue that suppresses growth hormone release, has shown promise in early feline studies and is used in humans with acromegaly. Availability and cost remain barriers in veterinary practice. Cabergoline, a dopamine agonist, has been used with limited effect. For most cats without access to radiation or surgery, medical management focuses on controlling diabetes as effectively as possible with high insulin doses, alongside monitoring for complications.
Complications and Associated Conditions
Cats with acromegaly are at elevated risk of several concurrent problems. Hypertrophic cardiomyopathy — thickening of the heart muscle — is common and results from the direct effects of growth hormone on cardiac tissue. Kidney disease tends to progress, partly due to the effects of persistent hyperglycaemia and partly due to pressure from enlarged abdominal organs. Neurological signs such as behavioural change, circling, or seizures can develop if the pituitary tumour grows large enough to compress surrounding brain tissue.
Arthritis and joint problems are also reported, consistent with the excessive soft tissue and bone changes driven by chronic growth hormone excess.
Quality of Life and Realistic Expectations
Without treatment targeting the underlying tumour, acromegaly in cats is a progressive condition. Median survival times in cats managed with insulin alone vary widely, but the disease typically progresses over months to a few years. With radiation therapy, survival times of two to four years post-treatment have been reported, and quality of life is often significantly better.
The conversation with your vet should centre on what is realistic for your cat specifically — their age, concurrent conditions, and your own capacity for intensive management. Even without specialist treatment, cats with acromegaly can be kept comfortable with careful diabetes management, regular monitoring, and proactive management of complications as they arise.