My cat seems to be big-boned, especially in his limbs and face. Recently he started urinating a lot more than usual; he is drinking a big quantity of water as well. The veterinarian diagnosed him as having diabetes. The doctor also detected congestive heart failure. He suspects my cat might have acromegaly and has arranged for a CT scan and some other tests. What is acromegaly and what causes it? Is it treatable?
Acromegaly is a condition affecting older male, and infrequently female, cats. Affected cats may have enlarged or overgrown limbs and jaws and are typically overweight. Acromegaly, which is also called hypersomatotropism, is caused by excessive secretion of growth hormone (somatotropin). In cats, the excessive production and release of growth hormone is usually associated with tumors of the pituitary gland in the brain.
Growth hormone affects the body in two basic ways. Some tissues are built up, while others are broken down into molecular components. Growth hormone builds up muscle, bone, connective tissue and vital organs. When hypersomatotropism occurs, these tissues will overgrow, which accounts for the physical changes noted above in affected cats. Many affected cats will develop hypertrophic cardiomyopathy, or enlargement of the heart muscle. This eventually results in congestive heart failure (CHF). The liver and kidneys of an affected cat are likely to be enlarged also.
Growth hormone also causes the breakdown of fat and stored sugar in the liver. Excessive growth hormone secretion causes metabolic problems that result in persistently high, abnormal blood sugar levels and diabetes mellitus. Affected cats will drink and urinate excessively.
Diagnosis may require special laboratory tests and a CT scan of the head. The scan will help identify the presence of the pituitary gland tumor and its size and location.
Congestive heart failure, diabetes, kidney disease and other conditions resulting from the excess growth hormone will be treated concurrent with therapy for the pituitary tumor. Tumor treatment may include surgery to remove or debulk (reduce the size) the tumor, various medications to interfere with growth hormone's actions, and radiation. Unfortunately, clinical experience with these treatment methods is insufficient to determine their individual or combined efficacies at this time.
The prognosis for cats with acromegaly is guarded to poor. Many affected cats may die from tumor expansion. However, since a significant proportion of affected cats die of complications of kidney disease, CHF or diabetes rather than tumor expansion, aggressive treatment of these diseases may help improve survival times.
05/04/06
