Acromegaly is a hormonal disease of cats in which excessive growth hormone (GH) is produced from a tumor in the pituitary gland. Although previously considered to be rare, there is now evidence that acromegaly may be under-diagnosed in cats. One reason for this is that there are currently few effective therapies for feline acromegaly, and therefore veterinarians may not test for the disorder. Acromegaly is important in cats because it causes diabetes mellitus with severe insulin resistance. It also causes weight gain, enlarged organs, thickened bone and soft tissues, and heart and kidney disease. Cats with acromegaly often die or are euthanized because of heart or kidney disease, or the complications of uncontrollable diabetes mellitus. Acromegaly is diagnosed by measuring GH, and a related hormone called insulin-like growth factor-1 (IGF-1). The latter is responsible for tissue and organ growth in these patients. In this study we propose to evaluate a drug that is commonly used in human patients with acromegaly. The drug is a long-acting form of octreotide, which acts to decrease GH production from the pituitary tumor. This medication has not been previously evaluated in cats. The goals of the study are to determine if the medication safely reduces insulin dose, GH and IGF-1 levels in cats when given monthly for six months. The appropriate dose of the medication will also be determined. If effective, this medication will provide a more accessible therapy for cats with acromegaly and may increase awareness and diagnosis of this serious condition.