Ron Hines DVM PhD 4/28/06

This photograph is courtesy of Mr. Patrick Caro. Tumors of the pancreas are more common in ferrets than any other pet. The portions of the pancreas that are involved in the production of insulin are the islets. When a functional tissue of the islets, called beta cells, becomes cancerous the resulting tumor is called an insulinoma. Ferrets over the age of five are quite susceptible to this tumor which occur as small multiples or a single nodule within the pancreas a few millimeters in diameter. Understanding the effects of insulinomas requires understanding how glucose is burned as energy in cells throughout the body. In order for glucose to enter cells, a compound called insulin is required. Insulin is produced by the normal beta cells of the pancreas. When blood sugar level in the cells decline, insulin is released. Tumorous beta cells comprising the insulinomas release too much insulin and are oblivious to the glucose needs of body cells. This surplus of insulin causes blood sugar (glucose) to drop dangerously low (hypoglycemia).

Some researchers theorize that a diet rich in sugar may predispose ferrets to insulinomas much as a diet rich in sugar may predispose humans to diabetes. Others feel that the small gene pool from which the majority of US ferrets derive has caused this disease. If the sugar theory is correct it would be wise not to give your ferret sweet treats such as raisins, fruit, honey or semi-moist cat food.

Symptoms of Insulinoma
Insulinomas often occur when the ferrets reach 5-7 years of age. The first signs of insulinoma in ferrets is a detached, lackadaisical mood in which the ferret appears to be in a trance and is reluctant to move or interact with its natural curiosity. This progresses to lethargy and depression, weight loss, circling and difficulty using the rear legs. In advanced cases the ferret will twitch, faint and may have seizures. The majority of ferrets are not brought to a veterinarian until fainting and seizures occur. Ferrets in the midst of a low-glucose seizure can be helped with a bit of honey smeared on their tongue and in their mouth.

Diagnosis
The test to confirm insulinoma is a measurement of blood glucose in a ferret that has been fasting for 4-8 hours. Normal ferrets have a fasting blood glucose level of 85-125mg/decileter.
When blood glucose is lower than this, insulinoma is the most likely cause. If the test results are not dramatic (not under 70mg/ dl) a series of glucose tests should be scheduled. Results of 60mg/dl or less pretty much assure that a tumor is present. If you are concerned about insulinomas, one can have a fasting blood glucose test run every year on your ferret once it reaches the age of five.

Treatment
About half of the cases of insulinoma can be permanently cured with surgery. With surgery, diet control and medications ferrets with insulinomas usually live three or more years. If financial considerations make surgery prohibitive, your veterinarian can medically manage the tumors for a while. But because the medical management of insulinoma fails after a period of time, surgery early in the disease is the better option. Surgical removal of a portion of the pancreas is often successful in limiting the amount of insulin produced by the cancerous islet cells. In this surgery, diseased pancreatic islets and approximately half to two thirds of the normal-appearing pancreas is removed. Ferrets have a very large firm pancreas and the nodule or nodules of cancerous cells can be readily identified and pealed out. The result of successful surgery is a lowering of the amount of insulin produced. Occasional animals do not produce sufficient insulin after surgery and become diabetic.

Medications can control the low blood glucose of insulinoma for a limited period of time. The first line drug of choice is prednisone or prednisolone. It is given at 0.25-1.25mg/pound twice a day. Tablets can be crushed in berry juice or given in small portions. Prednisone increases blood sugar through its effects on the liver. It has a number of side effects, which in include weight gain, thin skin and possible cataracts and liver disease.

A second medication that can be given when prednisone fails is diazoxide (Proglycem Schering 2.5-5mg/pound twice a day), a drug given intravenously, to control high blood pressure in humans. The oral form is used to treat insulin-producing tumors in people. Diazoxide inhibits the release of insulin from the pancreas and also has a poorly understood extrapancreatic effect on blood sugar. Its effects last about 8 hours. Unwanted side effects in ferrets include fluid retention, diarrhea, appetite suppression and vomiting. Since it can also affect the formation of thrombocytes necessary for blood clotting, frequent blood tests are advisable. Retained uric acid caused by diazoxide has the potential of causing gout and cataract formation in humans has been reported. Also, this drug is quite expensive.

Mr. Tony Clarke brought to my attention an article concerning glucosamine sulphate published on page 251, vol. 357 of the Lancet. Glucosamine's affect on insulin and glucose levels might make it an effective tool in modulating hypoglycemia in inoperative cases of insulinoma in ferrets.

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