Glucagonoma in Dogs
Glucagonoma refers to a rare neoplasm (an abnormal growth of cells) of alpha-pancreatic islet cells that actively secrete glucagon, a hormone involved in the metabolism of carbohydrates. Many of these cells also secrete other hormones, such as insulin (a hormone largely involved in metabolism) and gastrin (a hormone that stimulates secretion of gastric acid in the stomach). The excess of glucagon circulating in the body can result in a number of responses, including an increased breakdown of proteins into amino acids (a process known as protein catabolism), and an increased breakdown of fat stored in fat sales (known as lipolysis).
Glucagonoma is an extremely rare form of neoplasm. It is uncommon in dogs, and is generally found only in older dogs. There are no known incidences of glucagonoma in cats.
Symptoms and Types
The signature symptom of glucagonoma, which has been reported in both humans and dogs, is a characteristic dermatitis, or skin abnormality. Skin lesions may include crusting and general erosions located around the mucus membranes on the face (moist tissues of the nose, for example) and genitalia. Lesions may also appear on the pads of the feet and other extremities. The footpads are often the only affected area, and are typically very painful.
This characteristic skin symptom associated with glucagonoma is also seen with liver disease and hypoaminoacidemia, a condition characterized by an abnormally low concentration of amino acids in the blood.
Additional symptoms of glucagonoma include sluggishness, diarrhea, weight loss, and incontinence. Secondary yeast infections are also common accompanying effects.
Glucagonoma can be seen in multiple endocrine neoplasia syndrome, an inherited disorder affecting the endocrine glands, which are responsible for releasing hormones into the blood stream. Solitary pancreatic glucagonoma (the formation of neoplasms in the pancreas), as well as cases of hepatic metastases, have also been reported in dogs.
A variety of tests may be used to help diagnose glucagonoma in dogs. These include a urine analysis, blood analysis (testing for amino acid, glucagon, and zinc levels), and ultrasounds, which may be used to detect irregular masses.
Ultimately, a tissue examination via biopsy, and chemical staining for glucagon presence, is necessary to definitively diagnose glucagonoma. Checking for the presence of other pancreatic and gastrointestinal hormones when staining is also advised.
Surgical removal of the neoplasm is the only method of cure. However, this may be risky as there is a high rate of post-operation death reported in dogs. Further, glucagonoma syndrome is associated with thromboembolic disease (in which a blood clot that has formed breaks free and moves through the blood stream to clot a blood vessel), which can occur postoperatively.
Hypoaminoacidemia, a condition associated with glucagonoma, in which an abnormally low concentration of amino acids is in the blood, may also occur concurrent with glucagonoma. A high-protein and egg white diet may help to deal with the effects of hypoaminoacidemia and thereby relieve related skin conditions. Zinc and fatty acid supplementation may also aid in relieving skin symptoms.
Medications, such as anti-yeast formulations or antibiotics, may be prescribed to treat secondary yeast or other infections that may develop in accordance with glucagonoma.
Living and Management
Following initial treatment, the patient’s blood work should be monitored regularly and follow-up ultrasounds should be performed to monitor for metastasis (in which the cell irregularity spreads to other parts of the body).