Insulinomas in Ferrets
By Emily Hoppmann, DVM
An insulinoma is a very common tumor of the pancreatic islet beta-cells, most commonly seen in ferrets older than two years of age of either sex. More specifically, it is a tumor that causes certain cells in the pancreas to secrete an excess amount of insulin. Insulin is necessary for normal cellular metabolism and maintenance of normal blood glucose levels. Excessive insulin secretion leads to too much glucose uptake and use by insulin-sensitive tissue and reduced liver production of glucose. This results in blood glucose levels dropping to dangerously low levels and can cause life threatening emergencies.
The systems in the body affected by an insulinoma include the nervous system, the musculoskeletal system, and the gastrointestinal system. When these systems are affected, it causes clinical signs such as lethargy, collapse, unresponsiveness or confusion, hind end weakness (often seen as walking normally on the front legs, but seeming to have no control over the back legs), muscle tremors, chronic weight loss, vomiting, nausea, and excess salivation. Pawing at the mouth, seizures, along with star gazing or glassy eyes are also commonly seen signs. The signs typically coincide with your ferret having an episode of low blood sugar and may or may not be related to eating or not eating, excitement, or exercise. Often times signs are not seen and so when an owner first witnesses any of these issues, it seems like the problem must have just started when it may have been going on for some time.
If you do notice any of the signs mentioned above, you should apply Karo-syrup (which can be found at any grocery store) or sugar water to the gums and rub it in to raise blood glucose levels quickly. After you have done this, you want to follow elevating the blood glucose levels quickly with feeding a high protein meal such as Hill’s A/D, Clinicare liquid diet for cats, Carnivore Care powdered diet (which you add water to in order to syringe feed) or pureed ferret pellets. You also want to seek immediate veterinary attention since low blood sugar can develop into a life threatening emergency and leaving an insulinoma untreated will allow for more of these life threatening episodes to occur.
Diagnosis of an insulinoma is usually based on the history of clinical signs seen at home (unless the veterinarian is able to witness the ferret having an episode), the physical exam findings, digital radiographs and/or ultrasound, and by blood work (such as the patients’ blood glucose level). In some cases, the blood glucose level may need to be repeated after a one to two hour fasting period (where the patient is not allowed to eat or drink at all) to document any changes in the blood glucose in relationship to food.
The good news is that an insulinoma is a highly treatable tumor with management including both medical and surgical options. Medical management is the most common option in patients with insulinomas because there is a high recurrence rate so surgery is not usually a permanent cure and carries risks. However, there are times that surgery is recommended to decrease the size of the tumor.
Medical management involves lifelong administration of oral steroids and, again, is the treatment of choice for insulinoma in ferrets. Steroids help regulate blood glucose and prevent the serious, even fatal, drops in blood glucose levels. Dietary management also plays a significant role in the treatment of insulinoma because eating a diet that is high in protein helps the body to maintain a higher, more consistent glucose level. By eliminating all simple sugars and treats from the diet and only feeding high protein ferret specific food helps to prevent excessive insulin release. Too much insulin in the body causes the glucose level to drop to dangerous levels, so the change in diet is all centered on keeping the insulin level low and the glucose level normal.
The prognosis for ferrets with insulinomas is typically good. However, since medical therapy is aimed at regulation of blood glucose levels and not reduction of tumor size, the dose of the medication will have to be adjusted over the lifetime of the patient. This is due to the fact that higher doses of steroids will be needed as the tumor grows. In most cases, the dose needs to be adjusted every six months but this is determined through routine follow-up examinations, documentation by the owner of clinical signs, and how the patient is doing overall.