Insulinomas in Ferrets

Katrina D. Ramsell Ph.D, DVM

(Revised March 2003)

This is an extremely important topic as it is one of the most common diseases that many middle-aged to older ferrets are diagnosed with.  It is a disease that can occur alone or in conjunction with other health problems commonly seen in ferrets.

What are insulinomas?

Insulin is a hormone that is normally produced by beta cells in the pancreas.  Insulinomas are cancerous growths of beta cells which produce abnormally high levels of insulin.  Insulin normally helps the body move glucose (a sugar) from the bloodstream into cells for storage. When insulinomas are present, too much glucose is removed from the circulating blood, and blood sugar levels can drop to dangerously low levels (hypoglycemia).  There are certain organs, such as the brain, which require glucose to function properly.  When the brain is relatively “starved” of glucose, it can have problems functioning correctly and can behave in an erratic manner.  Most of the signs that we see associated with insulinomas come from the brain functioning abnormally.  Early in the disease, the ferret’s body counteracts the drop in blood sugar levels by producing more sugar from the liver.  This can temporarily correct the problem, so the symptoms of the disease may initially be very subtle.  As the disease progresses, the body is less able to compensate for the low blood sugar levels and the signs become more severe and last longer.  Although most (approximately 95%) insulinomas are malignant (islet cell carcinomas) and have the potential to metastasize (spread to other organs), most insulinoma tumors do not act aggressively or spread.

What are the symptoms of insulinomas?

Signs of the disease may come on gradually over a period of weeks or even months, and they may be very subtle at first.  You may notice that your ferret is sleeping more or is a little more difficult to awaken from naps.  Sometimes ferrets will appear to stare off blankly into space or bob their heads a little.  As the disease progresses and the signs become more obvious, you may observe your ferret falling over or seeming weak, especially in the hind end.  You may also see drooling or pawing at the mouth, which are both signs likely associated with the feeling of nausea when the blood sugar drops.  More severe signs can include extreme lethargy, seizures, or even a comatose state.  Sometimes people will find their ferrets unconscious with feces or urine present, as they can lose bowel or bladder control during a low blood sugar episode.  The ferret may feel cool to the touch.  If your ferret is ever seizuring or in a coma, it is a dire emergency, and you should seek immediate medical attention for your pet!

How are insulinomas diagnosed?

The most common way of diagnosing insulinomas is by measuring blood glucose levels.  If a ferret is not exhibiting severe signs and is stable, then a fasting blood glucose level is more accurate for diagnostic purposes.  Ferrets are usually fasted for approximately 4 hours for this blood test.  Occasionally blood insulin levels are also checked at the same time.  If your ferret is having any other problems, such as diarrhea or weight loss, then a complete blood panel is recommended.  Severe infections can sometimes result in bacteria in the blood (sepsis) which can consume glucose and drive blood sugar levels down.  Although this is a much less common cause of abnormally low blood glucose levels, a severe infection can show up on a blood panel.  Determining whether your ferret has insulinomas and/or a severe infection will aid in making sure that your ferret is treated appropriately.  Another less common reason your ferret may have low glucose levels is if the liver is diseased or damaged.  The liver is an organ with many functions, and one of those functions is to produce glucose for the body.  Certain diseases and some toxins can hinder the liver’s ability to produce glucose.  Blood tests to evaluate the liver can help determine if the liver is not functioning properly.  X-rays and ultrasounds are not helpful in identifying insulinomas present in the pancreas, but they may be helpful if it is suspected that the cancer has spread to other organs.  Note: Insulinomas are slow growing tumors and signs of this disease typically progress slowly.  If your ferret suddenly is having significant problems with hypoglycemia, but never had symptoms before, then it is likely another illness has occurred which decreased your pet’s appetite.  This will greatly worsen any previous hypoglycemia which an insulinoma may have been causing and may cause the insulinoma to “show itself”.  In these cases, treatment of the more recent illness (to restore normal appetite) may allow the blood glucose to rise enough that once again there are no obvious signs of hypoglycemia (until the insulinoma becomes larger).

What is the treatment for insulinomas?

Treatment of this disease depends on the stage of the disease and the overall condition of the ferret.  Surgery is usually the treatment of choice for this disease.  Insulinoma tumors can often be surgically removed and further medication may be unnecessary, or at least delayed for a period of time. If surgery is not possible for whatever reason, or in cases where the disease returns after surgery, then dietary and medical management is usually necessary.  Dietary management of insulinomas requires providing your ferret with a good quality, high protein diet at all times. Treats should generally be minimized, but if they are given, they should be high in protein such as cooked egg or strained meat baby food.  It is important to make sure that your ferret eats at least every four to six hours.  NO SUGARY TREATS should be given.  This will only exacerbate the disease by stimulating release of more insulin from the pancreas.  Ferrets with insulinomas often appear stronger and more alert after eating a meal.  When diet no longer controls the signs of the disease, then the ferret may have to be put on a corticosteroid, such as prednisolone (a drug that increases blood glucose levels), and/or a drug called diazoxide (Proglycem) (a drug that inhibits insulin release from the pancreas).  Previous reports have suggested that chromium picolinate and Brewer’s yeast (a substance containing chromium) may help stabilize blood glucose levels in diabetic patients and in ferrets with insulinomas.  However, there is currently no evidence to support that chromium is beneficial to insulinoma patients, and use of these chromium containing products could potentially even be harmful to ferrets with insulinomas.

Although insulinoma surgery can be relatively expensive, surgical removal of the tumors is preferred to long term medial therapy for several reasons: 1) Surgically removing the insulinomas can eliminate the primary cause of the high insulin levels rather than just treating the symptoms (altering insulin and glucose levels in the body with drugs); 2)  Individual insulinoma tumors can usually be removed completely with surgery if they are large enough to see and/or feel when the surgeon is checking the pancreas for tumors; 3) Long term use of corticosteroids, such as prednisolone, can cause side effects such as muscle wasting, a pot bellied appearance from fat accumulation in the abdomen, and irritation to the stomach which can become severe and result in stomach ulcers; 4) As the amount of drugs needed to control the insulin and glucose levels gradually increases, the risk that there will be toxic side effects to your ferret also increases; 5) Diazoxide is a relatively expensive drug.

EMERGENCY TREATMENT: If your ferret is seizuring or having a hypoglycemic attack (mentally non-responsive, drooling/foaming from the mouth, etc), rub some Karo syrup on your ferrets gums. You may want to use something like a Q-tip to apply the Karo syrup because your ferret may accidently bite your finger while in this confused state.  If you have no Karo syrup, mix up some concentrated sugar water and apply it to the ferret’s gums.  You should then get your ferret to a ferret knowledgeable veterinarian or emergency clinic for further medical treatment and diagnostics.

Why do ferrets commonly get insulinomas?

Unfortunately we do not know the exact cause for this common disease in ferrets.  Ferrets are most likely genetically predisposed to get insulinomas, and a study is just getting underway to investigate genes that are potentially contributing to this disease and other common ferret diseases such as adrenal disease, inflammatory bowel disease, and lymphoma. Environmental or dietary factors may also influence the occurrence of insulinomas in ferrets.  It is possible that today’s ferret diets are too high in carbohydrates, which can potentially cause the pancreas to be overworked and encourage insulinomas to form.  More research needs to be done to ensure that the ferret diets we are offering them are truly appropriate for their little bodies.

What is the long term prognosis for ferrets with insulinomas?

Prognosis of ferrets with insulinoma disease depends on the age of the ferret, whether or not the tumor has spread (this is uncommon), what kind of treatment the ferret receives, and if the ferret has suffered any brain damage due to seizures.  Some ferrets do fine after having surgery where one or more insulinomas are removed from the pancreas, but new tumors may arise and the signs often return after a period of time. Unfortunately the tumors aren’t always large and easily removable with surgery.  Sometimes there are tiny tumors in the pancreas too small to see or feel.  If this is the case, during surgery a portion of the pancreas may be removed to decrease the amount of pancreatic tissue and help decrease the amount of insulin produced.  Most insulinomas can be managed with surgery or medications for months or even years; the disease is often chronic, but it is rarely fatal by itself. The best prognosis is for ferrets that have only a few isolated tumors (with no spread of the disease throughout the pancreas or to other organs) and very early diagnosis.  The worst prognosis is for ferrets that have many insulinomas developing or have aggressive tumors that have metastasized to the rest of the pancreas and other organs.

As ferrets are prone to have many rather serious health conditions, especially as they age, it is important that you are aware of signs associated with each of the common ferret diseases.  It is also important that your ferret visit a ferret knowledgeable veterinarian each year, and twice a year once your ferret is over 3 years of age.  Annual blood screens starting at the age of 3 can also help catch diseases early on, and this may result in prolonging and improving the life of your furry little buddy.  It is also important to make sure that your ferret is eating, drinking, urinating, defecating, and acting normally.  If you have any doubt then you should have your ferret examined.  With good care and preventive medicine, more ferrets are living past 8 years of age than ever before.