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Written by Dr. Bruce Williams, DVM:
The following article may be reprinted by anyone desiring to disseminate this information in a newsletter or non-commercial publication. This material may not be altered or changed in any way. Under Title 17 of the U.S. Code, Section 105, copyright protection is not available for any work of the United States Government.
Islet cell tumors, also known as insulinomas, are the most common neoplasm in the ferret, based on the frequency of surgical and autopsy submissions at the Armed Forces Institute of Pathology. Over a period of two and a half years, this neoplasm alone has accounted for almost 15% of all ferret submissions.
Islet cell tumors derive their name from their cell of origin. These neoplasms arise in the "islets of Langerhans" - a group of special cells in the pancreas which produce insulin (also giving rise to the term insulinoma). Insulin is a hormone which allows most of the cells in the body to utilize the glucose in the blood. The excess levels of insulin produced by these tumors drive the glucose in the blood into the cells of the body, causing a dangerously low blood glucose level, known as hypoglycemia. (In diabetes, the opposite is true - low levels of insulin production render the animal's cells unable to use glucose, and dangerous hyperglycemia results).
Not all islet cell tumors appear to be functional, however. Islet cell tumors are often found as incidental findings at autopsy of animals dying of unrelated causes. Finally, a small percentage of animals fail to show characteristic signs of hypoglycemia, or show signs that are so subtle that they are not noticed by the owner and picked up on routine blood screening for other conditions.
Hypoglycemic ferrets may exhibit a wide range of clinical signs. Weight loss appears to be a common finding in affected animals, and is occasionally the only sign. This is an excellent reason why you should periodically weigh your pet as part of a good preventive health program. Signs that are more diagnostic of islet cell tumors are episodic depression and lethargy, which in some animals manifests as stupor (apparent loss of touch with its surroundings), salivation, difficulty in using the hind legs, vocalization, and in cases of severe hypoglycemia, seizures.
Diagnosis of islet cell tumors is fairly simple and consists primarily of measuring the blood glucose levels in the ferret, which your vet can do if you suspected this problem. (Some vets additionally measure insulin levels, but in most cases, this is unnecessary and wastes valuable time.) Animals with blood glucose levels less than 60 mg/dl should be strongly suspect of having one or more of these tumors. Exploratory surgery in hypoglycemic but otherwise healthy ferrets should be scheduled at the earliest possible time.
In animals where surgery is not an option, or until such a time as surgery is possible, medical management may be attempted by using a combination of prednisone (which raises blood glucose levels by mobilizing carbohydrate stores) and diazoxide (Proglycem) an antihypertensive drug which appears to decrease islet cell secretion of insulin. It is important to realize that this is only a temporary measure and rarely is effective in controlling the animal's hypoglycemia for a long period..
It is also important to note that in a large number of cases (5/6 in one study), ferrets that had islet cell tumors surgically removed developed a second or more tumors at a later date. (Additionally, make sure that your veterinarian, if surgery is performed, takes a moment to check the adrenal glands for those extremely common proliferative lesions we so often see in ferrets.)
If you have a several ferrets, it is extremely likely that one of them, sometime during its life, will develop an islet cell tumor; it's the "nature of the beast". Just watch them closely for the clinical signs that I have described, and have your vet check them if you have even the slightest indication of a problem.
Happy ferreting!!!
Bruce Williams, DVM
1. Marini, RP et al. Functional islet cell tumor in six ferrets. JAVMA 202(3) 430-432, 1993.
2. Kawasaki, TA Personal communication.
In a different article, Dr. Williams cautions:
The largest number of insulinomas that I have ever seen is four. Ferrets get an age-related finding which is also seen in older cats known as pancreatic acinar hyperplasia. This is a non-neoplastic proliferation of small nodules in the pancreas, which are very normal. The problem is that while this nodular change is perfectly normal and doesn't hurt anything, many vets interpret it as a proliferation of islet cell tumors, and start taking them out. Now the ferret pancreas is fairly forgiving for surgery, but when you take out this many nodules, you stand a good chance of causing a rip-roaring pancreatitis.
Written by Dr. Susan Brown, DVM:
Insulinoma [is] a cancer of the pancreatic beta (insulin producing) cells. The tumors are very tiny, but produce an excessive amount of insulin which has the effect of driving the blood sugar (glucose) into the bodies cells at too rapid of a rate.
Some of the common signs that you might see are: Stopping and staring blankly into space (acting out of it) for a few minutes, then snapping out of it, or foaming and pawing at the mouth as if something is in it (caused by a feeling of nausea....this can also be caused by stomach problems like foreign bodies and ulcers, but those cases are usually not eating well on top of things...insulinoma generally does not interfere with eating habits), or just being weak in the hind end as was described in this case and then coming out of it, or going into a comatose state or even seizures. The more advanced the disease is the more frequent the signs and the more severe. As long as the body is able to it will keep counteracting the low glucose by producing more through the liver primarily...but eventually it will be unable to do so and the ferret may go into a permanent coma and pass away.
The disease is easily diagnosed with a FASTING blood sugar test. You need to withhold food for 4 to NO MORE THAN 6 hours prior to the test. This will show if the sugar is too low. Normal fasting sugar should be between 90-120. Your vet can also run an insulin level at the same time, but that is usually (in my experience) unnecessary.
Treatment may be a combination of surgery and medical therapy. The worst thing that you can do is give a lot of sugary snacks and treats. All this does is aggravate the condition by stimulating insulin production each time you give them a sugary snack which then results in insulin overload and hypoglycemia later. Use materials such as honey or Karo syrup in small amounts ONLY TO BRING THEM OUT OF A HYPOGLYCEMIC state and then as soon as they are swallowing normally and more alert, give them a protein snack such as strained meat baby food or their softened normal food. The protein keeps the glucose from jumping up and down.
It is also helpful to keep food always available and to add a supplement of Brewers Yeast to the diet. You can buy brewers yeast and garlic tablets for pets at health food stores or from you vet if they carry it. Or you can just buy plain Brewer's Yeast in a powder or tablet. Use 1/8 tsp of the powder twice a day, or 1/4 of a human tablet or 1/2 of a pet tablet twice daily. Brewers yeast contains chromium which is the glucose tolerance factor which helps to regulate insulin and glucose levels. These dietary suggestions will not CURE the pet, nor stop the cancer from growing, but they may alleviate some of the signs and prolong the amount of time the pet is off other medication.
Susan Brown, D.V.M.
Written by Dr. Blair Gustafson, DVM:
Insulinoma is a pancreatic tumor commonly found in ferrets. This tumor type usually shows up in ferrets 4-6 years old (so your ferret is a little young for this condition), but it can develop at any age, and I've seen insulinomas in ferrets as young as [a year or two].
This tumor type can sometimes be diagnosed with ultrasound, and this is a nice step to take prior to surgery because it is non-invasive, non-painful, and helps to confirm the diagnosis. If an insulinoma is diagnosed, you are correct that an exploratory surgery is required. While this tumor tends to metastasize or recur, if caught early enough, these little guys can sometimes be cured by excision of the tumor.
Dr. Mike Dutton, DVM, DACVP, writes:
My recommendations for ferrets with insulinoma:
1) surgically explore the pancreas and remove any obvious nodules and have them biopsied. (Unfortunately most insulinomas have microscopically metastasized by the time symptoms are noticed.) The removal of large tumors a) will make the ferret more manageable medically and b) may reduce the symptoms short term.
2) if still hypoglycemic or when becomes hypoglycemic again post-surgery, start on Prednisone. Start at a dose of 1/2 mg/kg once daily. You can increase this up to 2 mg/kg as needed. In my experience once you reach 2 mg/kg you have obtained maximum benefit from Prednisone. Increasing the dose won't do any more.
3) once maximum prednisone is reached, add diazoxide at the rate of 5 mg/ferret twice daily. You can increase this up to 30 mg/kg twice daily. Use in conjunction with prednisone.
4) If cannot manage the hypoglycemia anymore, can surgically explore the pancreas again. But you are now at the point of vastly diminishing prognosis.
Anecdotal stories talk about herbal remedies; however, none have been shown to work. Surgical removal of solitary tumors does buy some time for your pet. As for dying during the operation, it is unlikely but possible. Usually ferrets in good overall condition do well. A study from a couple of years ago stated that the average lifetime after a diagnosis of insulinoma and the surgical removal of a tumor was approximately 474 days.
So, if your ferret is doing not so well on the current dose of medication, try increasing it. If still no success, surgery may be an option. However, keep in mind that if the tumor is not solitary but spread throughout the pancreas, it may not buy you much time.
Meg Carpenter of Chaotic Ferrets adds:
Unfortunately, insulinoma can come on at any time, and the ferret risks going into a fatal seizure if his owner is not there to bring him around. It is hard on the poor baby to go through continuing attacks.
The proper management of insulinoma without surgery, treating with medication, should keep the ferret relatively free of attacks. If this is not the case, then surgery is the alternative. Of course, there is risk in having an operation. But with unmanaged insulinoma, you may lose the ferret without the surgery.
The first 48 hours after pancreatic surgery are the most critical, and intense management is needed, but in this area the survival rates are very good. What is generally found is a basal cell carcinoma of the pancreas.
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