Acromegaly in Cats

The pituitary gland is a pea-sized organ which sits at the base of the brain and regulates the expression of various hormones used for regular body function. These can include hormones for stress, metabolism, and growth. Growth hormones are utilized throughout the body to grow and maintain components. They are primarily used in childhood growth and development phases but are present in the body throughout life. A tumor affecting the pituitary gland can often cause an overstimulation of various hormones in the body, one of which being growth hormone, leading to acromegaly.

Acromegaly is uncommon in cats, and is most common in older, neutered males. Prognosis is good in the short term, but poorer as time goes on. This is a lifelong disease requiring intense medical management. The first signs noticed are usually those of uncontrolled diabetes mellitus, which warrant timely veterinary intervention on their own. Early diagnosis and treatment may improve long-term prognosis.

Symptoms vary in that they can be subtle or dramatic, and because the disease affects multiple organs/systems.

Neurological symptoms are uncommon and can include dullness, lethargy, abnormal behavior, circling, and blindness (bumping into objects).

Lameness is another potential, but uncommon, symptom.

The cause of acromegaly is excessive production of growth hormone by the pituitary gland due to the presence of a tumor. It is not known why this occurs in some cats.

Cases of acromegaly may be identified when a cat does not respond to treatment for diabetes mellitus, as the symptoms are similar.

The first step to diagnose a possible case of acromegaly is a physical exam and complete medical history. Blood work and urinalysis are also likely to be recommended. There is no single test for acromegaly. The condition is often suspected in diabetic cats who are not responding to the usual therapy (high-protein, low-carbohydrate diet and insulin). CT or MRI of the pituitary region are sometimes used to identify a pituitary tumor, and blood tests may confirm the diagnosis. Many cats with acromegaly are not diagnosed until after death.

Treatment options include medications, including insulin, surgery, radiation, and palliative care. Hypophysectomy (removal of the pituitary gland) may cause undesirable side effects. Radiation therapy may provide the best chance of successful treatment, however, pituitary tumors take 3+ years to shrink, so the potential for serious side effects is increased. Cats are often treated with increasing doses of insulin as a palliative measure. Regardless of the treatment, acromegaly is a lifelong disease for the cat.

Prognosis is fair to good in the short term, with symptoms being managed medically. The long-term prognosis is guarded to poor, as acromegaly eventually leads to organ failure (most commonly congestive heart failure secondary to hypertrophic cardiomyopathy). Early diagnosis and treatment may improve the outlook.

It is not known why some cats develop these growth hormone-secreting pituitary tumors, so specific prevention information is not available. Regular veterinary care can help catch symptoms early.

Acromegaly is uncommon, but probably underdiagnosed in cats with uncontrolled diabetes mellitus. Statistics show it is most common in middle-aged to older male neutered cats, but this may be biased because that is the same group most likely to be diagnosed with diabetes mellitus in the first place.

• Increasing doses of insulin
• Medications (Anti-growth-hormone drugs, Dopamine agonists)
• Hypophysectomy (removal of the pituitary gland)
• Radiation therapy