Insulinomas in Ferrets

Insulinomas are likely the most common tumor seen in pet ferrets. Also called pancreatic islet cell tumors, these are tumors of insulin-producing cells in the pancreas. The tumors produce an excess of insulin, which results in hypoglycemia (low blood sugar). Unfortunately, the tumors are often malignant, although they can usually be managed with surgery or medication for a significant length of time.

Insulinomas typically occur in ferrets around 2-3 years of age. The onset can be gradual, with signs starting mildly, then getting worse and more frequent; the illness can also be quite severe and sudden. Occasionally there are no obvious signs, and insulinoma is only discovered during lab testing done for other problems. Insulinoma can be found concurrently with adrenal disease, lymphomas, cardiomyopathy, and other diseases.

Signs of Insulinoma in Ferrets

The signs often occur in episodes, with periods of normal activity and behavior between episodes.

• Weight loss
• Episodes of depression, lethargy, being "out of it" (may even collapse and be unresponsive)
• Weakness and incoordination, especially of the hind legs
• Often salivation and pawing at the mouth during episodes
• Severe episodes can result in seizures, and occasionally coma
• Appetite often normal, sometimes decreased

Diagnosis

If your ferret shows any of these symptoms, a trip to a ferret-friendly veterinarian is a necessity. Diagnosis of insulinoma is most often based on clinical signs and low blood sugar (hypoglycemia), measured by a blood sample. Occasionally, blood testing may need to be repeated, or performed after a short wait (4 hours) to document low blood sugar. Some veterinarians also test insulin levels. Other tests are recommended to assess your ferret's overall health, and the possible presence of other diseases.

Treatment Options

Surgery

In an otherwise healthy ferret, the treatment of choice is surgery, which allows the removal of visible tumors (there are often multiple tumors). During surgery, your veterinarian should also check the adrenal glands for enlargement, as an adrenal disease may be present at the same time. Unfortunately, because of the nature of islet cell tumors, they often spread despite surgery making medical management necessary in the future. However, the surgery to remove larger tumors often alleviates the symptoms for some time, or at least makes medical management easier. Blood sugar should be tested at regular intervals (two weeks after surgery, then every couple of months), so medical management, if necessary, can begin.

Medical Mangement

Medical management may be needed after surgery or may be the treatment of choice for ferrets that are quite old or ill and therefore a poor surgical risk. The drugs prednisone and diazoxide can be used (alone or in combination), and while they help control the symptoms, they do not affect the progression of the disease. Dietary management is also important—make sure food is always available and provide a high-quality meat-based ferret diet (high in protein and low in carbohydrates). Additionally, sweet treats must be completely avoided as they can provoke a hypoglycemic episode (by stimulating the tumor cells to produce excessive amounts of insulin). Tips on emergency management of a hypoglycemic episode at home will also be provided by your veterinarian. Remember that medical management is only meant to help control the hypoglycemia, and that as the disease progresses, the symptoms may worsen. An increase in medication dosages is likely, but eventually, the medication may become ineffective.

Resources

• Ferret Insulinoma FAQ—Information from several ferret veterinarians (including Dr. Bruce Williams) on insulinoma signs, diagnosis, and treatment.
• Insulinoma - How to Recognize It and Emergency Treatment—a nice article that is not too clinical and provides lots of practical advice on dealing with a ferret who has an insulinoma. By Beth Camarow in consultation with Dr. Charles Weiss.