Acromegaly in Cats: Hormone Excess and Hard-to-Manage Diabetes

Some diabetic cats seem to defy every adjustment. Their insulin dose keeps climbing, yet they stay thirsty, hungry, and unwell, and some even gain weight when you would expect them to lose it. One possible reason is acromegaly, a hormone disorder in which a small growth in the pituitary gland releases too much growth hormone. Excess growth hormone works against insulin, which is why acromegaly so often shows up as diabetes that is hard to manage. This guide explains what acromegaly is, how it affects the body, the signs that warrant a veterinary exam, how veterinarians confirm it, the management options they may discuss, and how you can support your cat at home.

Important: This article shares general educational information for pet owners and is not a substitute for an in-person veterinary examination, diagnosis, or treatment. For any medical concern or emergency, contact your veterinarian promptly.

What Is Acromegaly in Cats?

The pituitary gland is a small structure at the base of the brain. It produces several hormones that direct other glands and tissues, including growth hormone. In a healthy adult cat, growth hormone helps regulate metabolism and the maintenance of body tissues.

Acromegaly, also called hypersomatotropism, develops when a pituitary tumor produces growth hormone in excess. These tumors are usually benign, meaning they do not typically spread to other parts of the body, but the hormone they release has effects throughout the body.

The role of IGF-1

Growth hormone prompts the liver and other tissues to make a second hormone called insulin-like growth factor, or IGF-1. IGF-1 drives the growth of bone, cartilage, soft tissue, and internal organs. A constant oversupply gradually enlarges the head, paws, and other tissues.

Why Acromegaly Makes Diabetes So Hard to Manage

Insulin moves glucose out of the bloodstream and into the cells that use it for energy. Growth hormone has the opposite effect on many tissues: it makes them less responsive to insulin. This is called insulin resistance.

When the pituitary keeps releasing growth hormone, the body may not be able to make enough insulin to overcome this resistance, and diabetes develops. Once a cat is diagnosed with diabetes, the same resistance means ordinary insulin doses often do not bring blood glucose into the target range. Your veterinarian may increase the dose step by step and still see high readings, persistent thirst, and frequent urination.

For this reason, veterinarians often consider acromegaly when a diabetic cat needs unusually high insulin doses, when glucose control swings unpredictably, or when a cat is not responding as expected. Our overview of diabetes in dogs and cats covers the basics of the disease and its daily care.

Not every hard-to-manage diabetic cat has acromegaly

Many things can make diabetes difficult to control, including infections, dental disease, inflammation, other hormone disorders, inconsistent insulin handling, and diet. Your veterinarian will usually look at these possibilities alongside acromegaly.

Which Cats Are Affected?

Acromegaly is most often recognized in middle-aged and older cats, and it is reported more often in males. It can occur in any breed, including mixed-breed cats.

Because its physical changes develop slowly, they often go unnoticed until diabetes prompts a closer look.

Acromegaly is far less common in dogs, and when it occurs in dogs it usually has different causes. This article focuses on cats.

Signs That Warrant a Veterinary Exam

Signs tend to develop gradually, and diabetes is usually noticed first.

Diabetes-related signs

• Increased thirst and urination: drinking more, larger clumps in the litter box, or accidents outside the box.
• Strong or increased appetite: a cat who seems constantly hungry.
• Weight gain or stable weight despite diabetes: poorly controlled diabetic cats usually lose weight, so gaining weight while diabetes stays uncontrolled is a notable clue.
• High or rising insulin needs: doses that keep increasing without the expected improvement.

Body and facial changes

• A broader face or head: the head may look larger or more square over time.
• Large paws: feet that seem wider or chunkier than before.
• A protruding lower jaw: the lower jaw may extend ahead of the upper jaw, and gaps between the teeth may widen.
• A larger tongue or thicker tissues in the mouth and throat.
• Stiffness or reluctance to jump: excess growth hormone can affect the joints.

Breathing and heart changes

Soft tissue in the throat and upper airway can thicken, which may lead to snoring or noisy breathing at rest. Learn more about snoring and noisy breathing in dogs and cats. Acromegaly can also be associated with thickening of the heart muscle and enlargement of organs such as the kidneys and liver. Labored, rapid, or open-mouth breathing is different: it needs care right away.

How Veterinarians Diagnose Acromegaly

Diagnosis usually combines history, physical findings, blood tests, and imaging.

1. History and physical exam: your veterinarian will ask about insulin doses, appetite, thirst, and weight, and will look for facial, jaw, paw, and organ changes.
2. Routine bloodwork and urinalysis: these help assess diabetes control and screen for other conditions that can interfere with insulin, such as infections or kidney changes.
3. IGF-1 blood test: a high IGF-1 level supports a diagnosis of acromegaly. In cats with newly diagnosed diabetes that have only recently started insulin, the result can be misleading, so your veterinarian may recommend repeating it later.
4. Imaging of the pituitary gland: a CT scan or MRI, performed under anesthesia, can show an enlarged pituitary gland or a pituitary mass.
5. Heart and chest evaluation: chest imaging or an echocardiogram may be suggested if a murmur, abnormal rhythm, or breathing changes are found.

Some cats are referred to a specialist for advanced imaging and planning.

Management Options Your Veterinarian May Discuss

The best approach depends on your cat's overall health, the size of the pituitary tumor, access to specialty centers, and your family's circumstances.

Pituitary surgery

Hypophysectomy is surgical removal of the pituitary gland. It is performed at a small number of specialty centers with specific expertise. When successful, it addresses the source of excess growth hormone, and some cats no longer need insulin afterward. Cats that undergo this surgery need replacement of hormones the pituitary normally controls, some of them for life and some only temporarily, given as prescribed by your veterinarian, and careful monitoring in the period after surgery.

Radiation therapy

Radiation therapy directed at the pituitary tumor is another option at specialty centers. It requires anesthesia for each session. The effect on growth hormone and insulin needs develops over time rather than right away, and the response varies between cats.

Medical management

Your veterinarian may discuss medications that act on growth hormone release, such as somatostatin analogs, given as prescribed by your veterinarian. Availability, cost, and the need for repeated injections influence whether this is practical.

Managing the diabetes

Many cats are managed with insulin alone, adjusted carefully by your veterinarian, along with a diet your veterinarian recommends. Close glucose monitoring is especially important because insulin needs can change, sometimes quickly, after surgery or radiation. If growth hormone levels fall, a previously high insulin dose can become too much.

Supporting Your Cat at Home

Home care works alongside your veterinarian's plan and never replaces it.

Keep every recheck appointment, even when your cat seems stable.

When to Call Your Veterinarian

Schedule a veterinary exam soon if your cat shows gradual changes, such as:

• Increased thirst, urination, or appetite that persists despite insulin
• Weight gain or stable weight while diabetes remains poorly controlled
• A broader face, larger paws, a protruding lower jaw, or widening gaps between the teeth
• New snoring or noisy breathing while your cat is otherwise breathing comfortably
• Stiffness, limping, or reluctance to jump

Contact your veterinarian or an emergency clinic right away if your cat

• Has labored, rapid, or open-mouth breathing
• Collapses, is very weak, or cannot stand
• Is wobbly, twitching, disoriented, or has a seizure, which can signal dangerously low blood sugar
• Is vomiting, refusing food, and very lethargic, which in a diabetic cat can signal diabetic ketoacidosis
• Suddenly cannot use the back legs or seems to be in severe pain

Read more about the warning signs of diabetic ketoacidosis in dogs and cats, a diabetic emergency that needs care right away.

Common Mistakes and Myths

Myth: If insulin is not working, the dose just needs to go higher.

Fact: raising the dose without looking for the cause can be risky. When a cat needs unusually high doses, your veterinarian may look for underlying causes such as acromegaly before adjusting further.

Mistake: Changing the insulin dose at home without guidance.

Fact: insulin needs in acromegalic cats can be unpredictable. Always speak with your veterinarian before any change, because too much insulin can cause dangerously low blood sugar.

Myth: A diabetic cat who is gaining weight must be well controlled.

Fact: in acromegaly, weight gain can happen even when diabetes is poorly controlled, so weight alone does not tell the full story.

Myth: A pituitary tumor always means the outlook is poor.

Fact: these tumors are usually benign, and many cats live comfortably with good diabetes management and regular monitoring. Your veterinarian can discuss what to expect for your cat.

Frequently Asked Questions

Is acromegaly painful for cats?

The tumor itself is not usually described as painful, but joint changes can cause stiffness and discomfort.

Can acromegaly go away?

Successful pituitary surgery can address the source of excess growth hormone, and some cats no longer need insulin afterward. Other approaches focus on managing hormone levels and diabetes over the long term.

Will my cat always need insulin?

It depends on the approach and the individual cat. Some cats no longer need insulin after surgery or radiation, while many cats managed with insulin alone continue to need it. Your veterinarian will guide any changes.

Can acromegaly affect cats that are not diabetic?

It is possible, but most cats are identified because of diabetes. Some cats with excess growth hormone may not yet show diabetes.

Is acromegaly contagious to other pets or people?

No. Acromegaly is caused by a pituitary tumor and cannot spread between pets or to people.

Key Takeaways

Acromegaly is a hormone disorder in which a usually benign pituitary tumor releases excess growth hormone. Growth hormone opposes insulin, so most affected cats develop diabetes that is hard to manage, often needing unusually high insulin doses. Signs that warrant a veterinary exam include persistent thirst and urination, a strong appetite, weight gain despite poorly controlled diabetes, a broader face, large paws, a protruding lower jaw, noisy breathing, and stiffness. Diagnosis usually relies on an IGF-1 blood test, often supported by CT or MRI imaging of the pituitary gland. Options your veterinarian may discuss include surgery or radiation therapy at specialty centers, medical management, and careful insulin management, all as prescribed by your veterinarian. Contact your veterinarian or an emergency clinic right away if your cat has labored or open-mouth breathing, collapses, is wobbly or has a seizure, or is vomiting, refusing food, and very lethargic.