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insulinoma

INSULINOMA (or pancreatic cancer)

BODY MECHANISM

The pancreas is an organ located within the abdomen, near the spleen and is responsible for secreting various hormones into the bloodstream, as well as pancreatic enzymes into the intestines to aid in digestion.

The beta cells within the pancreas, contain cells called the Islets of Langerhans - these are responsible for secreting the hormone, insulin.

Carbohydrates are long strings of sugar, and when a carbohydrate is digested, the sugar (glucose) enters the blood stream, waiting to be used. Insulin is then released from the pancreas in response to the increased “blood glucose” level, in order for the glucose to be utilised by the cells throughout the body.

In a healthy animal, blood glucose levels fluctuate moderately depending on when and what was last eaten.

Ferrets have a carbohydrate requirement of ZERO, which means they aren’t designed to digest large amounts of carbohydrates or sugar throughout their life, nor release the large amounts of insulin to deal with them. It is thought that the continued consumption of high amounts carbohydrates, over-stimulates the pancreas, and leads to the development of pancreatic neoplasms (cancers) also known as “insulinoma”.

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)

Other names for insulinoma include: Islet Cell Tumours (named after the Islets of Langerhans), beta cell tumours, pancreatic tumours, insulinomas, or insulinoma tumours.

Diabetes is very uncommon in ferrets, so it appears that their bodies react by developing neoplasms rather than burning out.

The excess levels of insulin produced by these pancreatic neoplasms (insulinoma) drive too much of the glucose in the blood into the cells of the body, causing a dangerously low blood glucose level known as hypoglycemia.

In the early stages of insulinoma, the bouts of hypoglycemia are sporadic, but as it progresses, the hypoglycemia becomes constant.

Dizziness, fatigue, headaches and shakiness are all effects of hypoglycemia that humans have reported, and ferrets probably feel similar.

In diabetes, the opposite is true - low levels of insulin production render the body’s cells unable to use glucose, resulting in hyperglycemia (high blood glucose level).

Glucose is essential for a cell’s survival, and “glucose starvation” resulting from hypoglycemia can cause permanent damage – especially to sensitive cells such as neurons in the brain.

SUMMARY

Insulinoma

* neoplasms cause excess insulin production
* drives too much glucose from the blood into cells
* results in hypoglycemia (low blood sugar)

Diabetes

* “burn out” results in low insulin production
* glucose in blood cannot be utilised by cells
* results in hyperglycemia (high blood sugar)

WORLDWIDE

In the USA, it is believed that pancreatic neoplasms (insulinoma) are the most common neoplasm in ferrets (#2), although exact figures are unknown. Most ferrets in the USA are fed primarily on processed foods containing high levels of carbohydrates (mainly ferret or cat biscuits). This is one of the reasons we do not recommend feeding your ferret any processed food, including biscuits.

In Australia, insulinoma is still uncommon, but is surfacing more than it once did. This could be due to owners and veterinarians becoming more knowledgeable, but the link between more owners feeding processed foods and our rate of insulinoma cannot be ignored.


SYMPTOMS

The first thing you will notice with an insulinomic ferret, is that they will
stop whatever they are doing and STARE INTO SPACE.

This is because of a sudden drop in their blood sugar level, which makes them feel dizzy.

This will only last for several seconds, and they will then continue on their way as if nothing happened.

Other symptoms can include

* weight loss
* hypersalivation (drooling)
* hind leg weakness (although this is a symptom of many problems in ferrets)
* lethargy
* lack of appetite, and
* pawing at the mouth.

If left untreated, or if the subtle symptoms are not noticed, it will eventually progress to SEIZURES – where the ferret is unresponsive and may twitch.

In severe cases, this may progress to screaming seizures – the ferret is not screaming in pain, but their vocal chords become active during the seizure - then eventually coma and death.

DIAGNOSIS

If a ferret is suspected of having insulinoma, a veterinarian can test their blood glucose level, via a blood test.

Normal blood glucose level is in the range of 90-125 mg/dL (4.95 Mmol/L - 6.88 Mmol/L) * see note at end of article about concentration measurements

“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)

Ferrets are not usually fasted before a blood test, as “the majority of insulinomic ferrets will exhibit hypoglycemia without fasting, and may be thrown into a crisis situation following a fast” (#4)

Some vets will diagnose insulinoma without a blood test, based on symptoms and a quick temporary recovery by administration of glucose.

EMERGENCY TREATMENT

If an insulinomic ferret doesn’t show any initial symptoms, you may be faced with a hypoglycemic seizure (and ferrets usually save their serious illnesses for when the vet hospital is closed, like midnight on a Saturday!).

Raising the blood glucose level of a ferret having a seizure is essential. This is done by applying something with a high sugar content directly to the gums.

DO use honey, sugar/water paste, or Karo Syrup (corn syrup) – all 3 have high amounts of simple sugars (< 80%)

DO apply to the gums with a cotton bud, where it can be absorbed without risk of inhalation into the lungs

DO apply every 10 minutes or so, and if possible on the way to the vet.

DON’T use Nutripet, as although it smells sweet, it contains only 20% simple sugars

DON’T try to get the ferret to drink or put anything down their throat while he/she is seizing – this can cause aspiration pneumonia by inhaling the fluid into the lungs.

This is an emergency treatment only, so the ferret should be taken to a ferret-knowledgeable vet as soon as possible, to discuss treatment options.

TREATMENT

The preferred treatment is surgical, where any visible tumours on the pancreas are removed. Part of the pancreas may also be removed (partial pancreatotomy).

Even if a ferret is showing little or no symptoms, an extremely low blood glucose level is often enough for a veterinarian to proceed with surgery (if the ferret is up to the surgery & the owner agrees to proceed)

Insulinoma tumours do not usually metastasize (spread to other areas of the body).

Complete removal of all tumours is not often possible because they can be microscopic, so the ferret may show symptoms again not long after their surgery. Dr. Bruce Williams says, “the incidence of recurrence of insulinoma after surgery is high, averaging about 40% over a 10 months span” (#4)

Although surgery is not always curative, it is the only possibility of a cure, so we recommend attempting it unless the ferret is not able to withstand surgery.

For non-surgical candidates, drugs can be given to control the symptoms, however they are not a cure, and have no effect on the neoplasms.

Prenisone is a steroid available in either tablet or liquid form. “Prednisone achieves its effects by causing breakdown of body protein and reformation into glucose by the liver (a process known as gluconeogenesis) and by decreasing the utilization of glucose by many body tissues.” (#4)

Prednisone (PRED-nis-own) is converted to Prednisolone (pred-NIS-o-loan) in the liver, so some ferrets may do better on Prednisolone than Prednisone, as it saves this extra step in processing.

Side effects can include weight gain, and over a long period, liver damage.

Brewer’s yeast (a product containing chromium) used to be recommended to help raise the blood glucose level, however it is no longer recommended, as it actually LOWERS the blood glucose level.

PREVENTION

A ferret’s natural diet contains virtually no carbohydrates, so providing a diet as close to this as possible (and hence low in carbohydrates) is probably the biggest contribution you can make to preventing insulinoma.

Treats with high amounts of sugar and/or carbohydrates (including sultanas and Nutripet) should be avoided or given very sparingly.

Ferrets are often placed on a low-carbohydrate diet AFTER they are diagnosed with insulinoma, however it makes much more sense to provide an appropriate diet to every ferret, in an effort to avoid such problems.

REFERENCES

1. “Rethinking the Ferret Diet”, Dr. Susan Brown, DVM

2. “Islet Cell Tumor in the Ferret”, Dr. Bruce Williams, DVM

3. “Ferrets, Rabbits & Rodents: Clinical Medicine & Surgery”, 1997

4. “Insulinoma in Ferrets”, Dr. Bruce Williams, DVM


CONCENTRATION MEASUREMENTS

All concentrations (blood glucose or otherwise) can be measured using weight (grams), or molecule count (moles).

Weight

Mg / dL (milligrams per decilitre)

Traditional unit for measuring
blood glucose


Molecule Count

Mmol / L (millimoles per litre)

SI (Systeme International) world standard unit for measuring blood glucose (used in most places except the USA).

A mole is 6.23 x 10^23 molecules

Written by Shona Whaite






 
Ferret Society of Canberra
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