Recent studies have suggested that presence of acromegaly, a collection of features often occurring together as a result of excess growth hormone (GH) production (hypersomatotropism), among cats with diabetes mellitus (DM) has been underestimated. Most cases are assumedly caused by a functional benign pituitary tumor. Excess GH can have various effects on cats, including direct anabolic and catabolic effects. GH decreases insulin sensitivity and through this mechanism often causes insulin-resistant DM. Polyuria and polydipsia are often present from uncontrolled DM; polyphagia is also seen but may be related to effects of GH on appetite. GH induces growth factor-1 (IGF-1) production; excess IGF-1 causes additional anabolic effects. The anabolic effects of excess GH and IGF-1 can cause gradual, marked physical changes including broad facial features, abdominal (organ) enlargement, prognathia, and clubbed paws. Hypersomatotropism should be considered in cats exhibiting weight gain despite poor diabetic control and should be included as a differential for insulin-resistant DM. Routine screening may be indicated for IGF-1 and/or feline serum GH of every diabetic cat. Contrast-enhanced CT and MRI are useful for visualization of a pituitary abnormality. Radiotherapy has been the preferred treatment, although such options as hypophysectomy are increasingly available. Some cats can be managed with high-dose insulin therapy alone; however, regular quality-of-life assessments are indicated.

Feline acromegaly is more common in cats than once thought. This review emphasized the importance of being open to this diagnosis, particularly in diabetic cats. Some cats do not demonstrate the physical changes associated with this disease. Although these changes remain important disease markers, they are not required to pursue the diagnosis of acromegaly. In addition, acromegaly can cause significantly diminished quality of life from insulin resistance and poorly regulated DM, as well as concurrent problems (eg, congestive heart failure).—Jennifer Ginn, DVM, DACVIM

Update on feline acromegaly. Niessen SJM. IN PRACT 35:2-6, 2013.