Insulinoma in the Domestic Ferret

Beta cell tumors, also known as insulinomas, are the most common neoplasm in ferrets. These tumors produce excessive amounts of insulin, causing dangerously low blood glucose levels. Unlike dogs or cats, insulinomas in ferrets don't usually metastasize. Although the cause is different, this condition is essentially the opposite of diabetes mellitus. Diabetes causes insufficient insulin to be produced, resulting in high blood glucose levels. Diabetes mellitus is uncommon in ferrets, though not unheard of, and it can be a transient condition after insulinoma surgery.

Some veterinarians feel that the high incidence of insulinoma in ferrets may be due to the high carbohydrate diet that ferrets are fed. Susan Brown, DVM says, “If normal beta cells are bombarded with higher than normal levels of glucose (which comes from carbohydrates) they can become hypertrophied (overactive) trying to keep up with insulin demand. If the high carbohydrate diet continues, the result may be a complete burnout of the cells, which is what happens when a pet or a person develops diet-induced diabetes. However, another possibility is that instead of the cells burning out, they go from hypertrophy to neoplasia (cancer). Neoplasia is an abnormal growth of cells and can be preceded by a hyperplastic condition. I would like to stress that this exact mechanism has not been scientifically proven in ferrets to date, but the scenario is entirely within the realm of possibility.” ⁽¹⁾

Surgery to remove visible tumors or a large portion of pancreas frequently does not result in a cure. Dr. Bruce Williams says, “the incidence of recurrence of insulinoma after surgery is high, averaging about 40% over a 10 months span.” Even after undergoing a partial pancreatectomy, some ferrets may not have any relief from low blood glucose levels. In some cases, with good care and a combination of medical and surgical treatment, or medical treatment alone, a ferret may be able to live with this condition for a number of years.

A normal fasting blood glucose level is in the range of 90-125 mg/dL (4.95 Mmol/L - 6.88 Mmol/L). According to Katherine Quesenberry, DVM, in Ferrets, Rabbits and Rodents - Clinical Medicine and Surgery --- “Ferrets with blood glucose concentrations lower than 70 mg/dL (3.85 Mmol/L) are suspected of having Insulinoma. In one study of 49 ferrets with confirmed insulinoma, all had blood glucose concentrations lower than 60 mg/dL (3.30 Mmol/L).” Ferrets can often have shockingly low blood glucose levels and have no significant symptoms. Though I have no medical evidence to back this up, I believe this may be due in part to the ferret becoming acclimated to glucose levels that have been decreasing gradually over a period of time.

The excess levels of insulin produced by these pancreatic tumors drive the glucose in the blood into the cells of the body, causing a dangerously low blood glucose level known as hypoglycemia and can result in one or more of the following symptoms:

It's important that a hypoglycemic ferret eats regular, high protein meals to help avoid hypoglycemic episodes. Avoid foods with high sugar or carbohydrate (cereal) content. In end stage insulinoma, sugar may be the only thing that will allow a ferret to remain seizure free; however, in early stage Insulinoma, sugar may result in a see saw effect with blood sugar levels.

Emergency Treatment for Hypoglycemic Seizures
Contact your vet immediately after beginning this treatment!

Seizures brought on by the sudden drop in blood sugar levels can be a very frightening experience. Even the experienced ferret caretaker can feel helpless and in a panic. For many, the term seizure presents a picture of someone on the floor, twitching with arms and legs flailing around. This is usually not what you will see in a ferret that is in the midst of a hypoglycemic seizure.

In most cases, ferrets that are in this state are simply unresponsive and appear to be in a coma like state. They may have moments of rapid breathing and have repeated reactions that make them appear to be gasping for air. There may be some twitching or paddling with their legs. In severe cases, they may even scream, and though this is very difficult to hear and witness, rest assured this is not a pain response and the ferret is totally unaware of what is going on.

Treatment consists of quickly getting the ferret's blood sugar levels back up. The quickest way to do this is with a dextrose IV. Since this must be given intravenously, not subcutaneously, this is not something that can be done at home. Unfortunately, these attacks always seem to happen when the vet clinic is closed. Besides, in less severe cases, you can probably bring the ferret around quicker by starting home treatment immediately rather than racing off to the clinic unless it is open and right around the corner. Begin treatment while someone else calls the vet or emergency clinic, or if you are alone, begin the treatment and while waiting for the ferret to respond, make the call.

Home treatment consists of repeatedly painting the ferrets gums with Karo syrup using a Q-tip. I have found that Karo syrup works better than honey or Nutrical and thinning the Karo slightly with a bit of water seems to make it more readily absorbed. Applying Karo syrup one time to the ferret's gums and waiting for the ferret to wake up is usually not going to be very effective. You must repeatedly apply Karo every 20-30 minutes or so until the ferret starts to come around. Many say that the ferret will begin to respond in 5 or 10 minutes, and in some instances, this is true; however I have not found this to be the case if the ferret is unconscious. Many times it has taken an hour or more before the ferret responds.

Once the ferret is alert again, it's important to feed him or her a high protein meal to help stabilize his or her blood glucose levels. Chicken baby food works best for this and anyone with a ferret prone to low blood glucose episodes should always have some of this on hand, in addition to Karo syrup.

When you are done feeding the ferret, BE SURE to thoroughly wash off any karo syrup that has gotten on the fur or skin around the ferret's mouth. If not cleaned off, it can cause intense itching and the ferret may scratch to the point of bleeding.