Insulinomas are tumors within the pancreas that produce excess insulin and are one of the most common neoplastic diseases affecting ferrets. In the normal ferret, as in other mammals (including humans), the beta cells in the pancreas are responsible for producing a hormone known as insulin. Insulin is responsible for keeping the body’s sugar (glucose) levels in balance. Most of us are familiar with diabetes; where not enough insulin is produced and the diabetic patient has a very high blood glucose level. Think of insulinoma as the opposite of diabetes – excess insulin produced by tumor cells in the pancreas results in a low blood sugar (hypoglycemia).
Insulinoma may affect ferrets between the ages of 2 and 3 years, but is most commonly diagnosed in ferrets 4 to 5 years of age. The severity of clinical signs shown by the affected ferret varies with how fast these tumors develop and how long they have been present. Some ferrets develop a sudden onset of severe hypoglycemia, and the resulting low blood sugar will cause the ferret to collapse into a weakened, non-responsive state.
In other ferrets, the onset of hypoglycemia is more gradual. The ferret will demonstrate intermittent signs of disease varying from periodic inactivity, depression and rear limb weakness to hypersalivation and pawing at the mouth. If the blood sugar drops very rapidly, the ferret may have tremors, seizures or go into a coma due to the lack of glucose in the brain.
A diagnosis is usually made by associating the above clinical signs with a low blood glucose. Most veterinarians agree that a fasting blood glucose level less than 60 mg/dl is very suggestive of insulinoma. We will want to rule out other causes of hypoglycemia which include: anorexia/starvation, severe vomiting and diarrhea, a critical bacterial infection and liver disease. Measurement of the ferret’s serum insulin level may also be recommended to help with the diagnosis, but results are not always conclusive.
If your ferret is showing signs of severe hypoglycemia (weakness, collapse) you can rub honey or corn syrup onto his gums. Once he has improved, feed him some of his regular diet and then schedule an appointment with us.
Long-term treatment recommendations for insulinoma include surgery, medical therapy and dietary modification. The choice of therapy depends on the severity of clinical signs, the age and overall health of the ferret and owner preference. Medical therapy involves the daily administration of drugs that will help the body produce more glucose and use it more efficiently. Most veterinarians start with twice daily diazoxide (Proglycem), and adjust the dose in response to the ferret’s blood glucose levels, as well as how the ferret is doing clinically. If control is poor another medication, prednisolone, can be added to the regimen.
In addition, ferrets with insulinoma should be fed many small meals throughout the day. A diet containing high quality protein and moderate levels of fat is preferred. Food with processed sugar or high levels of simple carbohydrates (such as fruit, semi moist cat food, cookies, etc.) should be avoided.
Lastly, surgery can be performed where the tumor producing cells in the pancreas are removed. Many times the insulin producing tumor is throughout the pancreas, therefore if obvious tumor nodules are not found, a partial resection of the pancreas is performed.
Keep in mind that with any of the treatment options discussed above, ferrets with insulinoma are not cured, but rather controlled, and that blood glucose concentrations will need to be checked periodically. When treatment regimens are followed, many ferrets will continue with a good quality of life for one or more years.