Serious severity

Acromegaly (Hypersomatotropism)

A hormonal disorder of older cats in which a benign tumour of the pituitary gland pours out excess growth hormone. It is an under-recognised cause of diabetes that resists treatment, and over time it slowly enlarges the head, paws, and internal organs.

⚠️ Common symptoms

Diabetes that is very hard to control despite large and rising insulin dosesIncreased thirst, urination, appetite and, often, weight gain rather than lossA gradual broadening of the face and enlargement of the paws over monthsWider spacing of the teeth and an enlarging jawA pot-bellied appearance and enlarged organs (heart, kidneys, liver)In advanced cases, breathlessness, heart disease, or neurological signs

Acromegaly — also called hypersomatotropism — is a hormonal disease of older cats that is far more common than it was once thought to be. At its root is a small, benign tumour of the pituitary gland, deep at the base of the brain, which secretes too much growth hormone. That single hormonal excess sets off two very different kinds of trouble: a metabolic problem and a structural one.

The metabolic problem usually comes first and is how most cases are discovered. Excess growth hormone makes the body's tissues resistant to insulin, so an affected cat develops diabetes that is remarkably hard to control. Vets often suspect acromegaly precisely because a diabetic cat needs ever-larger doses of insulin and still runs high blood sugars, sometimes while gaining rather than losing weight. Measuring a blood marker called IGF-1, along with imaging of the pituitary, helps confirm the diagnosis.

The structural changes are slower and easy to miss because they creep in gradually. Over months the surplus growth hormone thickens bone and soft tissue: the face broadens, the paws and jaw enlarge, the teeth may space apart, and the heart, kidneys, and liver grow bigger, which can lead to heart disease and kidney failure in time. Owners rarely notice the reshaping day to day, and often only see it looking back at old photographs.

The most successful treatments tackle the tumour itself — radiation therapy, or removal of the pituitary gland at specialist centres, which can cure the diabetes as well. Where that is not an option, cats are managed with high, carefully titrated insulin doses and treatment of the secondary heart and kidney problems. Recognising acromegaly early, before the organ changes advance, gives the best chance of a good outcome.

🔍 Causes

Acromegaly is almost always caused by a benign, slow-growing tumour (an adenoma) of the pituitary gland at the base of the brain, which secretes excessive growth hormone. The surplus growth hormone drives insulin resistance — producing a difficult, insulin-resistant diabetes — and, over time, stimulates the overgrowth of bone, connective tissue, and internal organs. It is chiefly a disease of middle-aged to older cats and is more common in males.

🛡 Prevention

There is no known way to prevent acromegaly, as it arises from a spontaneous pituitary tumour. The key is early recognition: testing a growth-hormone-related marker (IGF-1) in diabetic cats whose blood sugar cannot be controlled allows the condition to be identified and treated before the physical changes and organ damage become advanced.

💊 Treatment

The most effective treatment targets the pituitary tumour directly — either radiation therapy or, at specialist centres, surgical removal of the gland (hypophysectomy), which can resolve both the acromegaly and the associated diabetes. Where advanced treatment is not possible, care focuses on managing the diabetes with high, carefully adjusted insulin doses and treating the knock-on heart and kidney disease.

When to see a vet: Raise it with your vet if a diabetic cat needs steadily larger insulin doses yet stays poorly controlled, or if you notice a broadening face, enlarging paws, or a pot-bellied shape in an older cat. These are the clues that prompt testing for excess growth hormone.

⚕️ Medical disclaimer

  • This information is educational only and is not a substitute for veterinary advice.
  • Symptoms overlap between conditions — only a vet can diagnose accurately.
  • Never withhold treatment or self-medicate based on information found online.
  • When in doubt, call your vet. Early intervention almost always leads to better outcomes.

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