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.