Insulinoma (Pancreatic Tumor) Guide

ImmunityDiseasesMeongsiljang Veterinary Advisory Board

Canine insulinomas are tumors in the pancreas that secrete excessive amounts of insulin. Hypoglycemic seizures and collapse are hallmark signs, and surgery is the most effective treatment.

What is Insulinoma?

Insulinoma in dogs is a functional neuroendocrine tumor that arises from the beta cells of the pancreas and causes excessive insulin secretion. The most critical aspect of management is controlling hypoglycemia. If your dog repeatedly shows signs such as collapse, seizures, or hindlimb weakness, fasting blood glucose testing is essential. Although insulinomas may appear benign histologically, they typically follow a malignant course; however, early surgical intervention, such as partial pancreatectomy, can effectively manage symptoms for an extended period. Insulinoma is recognized as the most common functional neuroendocrine tumor in dogs, making it vital not to overlook signs of hypoglycemia.

Causes and Pathogenesis

Insulinoma is a functional tumor that arises from the abnormal proliferation of pancreatic islet cells (beta cells). While a healthy pancreas stops secreting insulin when blood sugar levels drop, tumor cells continue to release insulin regardless of blood glucose levels. This leads to severe, recurrent hypoglycemia, even during fasting states. Insulinoma is the most common functional neuroendocrine tumor in dogs, typically follows a malignant course, and has a strong tendency to metastasize, particularly to the liver and regional lymph nodes. Based on current veterinary textbooks, there is no established evidence linking specific breeds or clear genetic causes to this condition.

Symptoms to Watch For

In the early stages, symptoms are often vague and easily mistaken for normal aging. If you notice any of the following signs recurring, please have your pet checked. - Lethargy: Your pet may sit down during walks or tire quickly. - Weakness in the hind legs: Sudden stumbling or collapsing. - Seizures or convulsions: Loss of consciousness or involuntary body jerking. - Behavioral changes: Standing dazed or failing to respond when called. - Changes in appetite: Showing hunger but becoming lethargic after eating. - Worsening on an empty stomach: Symptoms intensify when the time between meals is extended.

A senior dog lying listlessly with its owner

Emergency Signs Requiring Immediate Veterinary Care

Hypoglycemic seizures can lead to brain damage. If any of the following occur, immediately apply honey or sugar water to the gums and seek veterinary care right away: - Seizures lasting more than 5 minutes - Failure to regain consciousness - Two or more seizure episodes in a single day - Decreased body temperature and weakened breathing

How is it Diagnosed?

The key to diagnosis is confirming both fasting hypoglycemia and inappropriately elevated insulin levels. In the clinic, tests are typically performed in the following order: - Fasting blood glucose test: Blood glucose is measured after fasting. If hypoglycemia occurs only intermittently, fasting may be required for up to 72 hours. - Insulin-to-glucose ratio assessment: If insulin levels are inappropriately high despite hypoglycemia, insulinoma is strongly suspected. - Abdominal ultrasound: This checks for pancreatic tumors and liver metastasis, but small tumors may be missed; imaging sensitivity is reported to be around 50%. - CT scan: This provides a more sensitive evaluation of small lesions and the extent of lymph node metastasis. If you’d like to learn more about the testing process, please refer to our Dog CT Scan Guide.

How is Treatment Managed?

Treatment involves a combination of surgery, medication, and dietary management, with the specific approach determined step by step based on the patient’s condition and whether metastasis has occurred. - Surgery (partial pancreatectomy): This is the most effective treatment and significantly extends survival time. - Medication: If surgery is not feasible or if metastasis has occurred, diazoxide and prednisolone are used to manage hypoglycemia. - Dietary management: Feed small, frequent meals (4–6 times daily) to stabilize blood sugar levels. - Chemotherapy: This may be considered as an adjunctive treatment if metastasis has progressed. According to veterinary pharmacology textbooks, medication dosages are adjusted by the veterinarian based on the patient’s response.

A veterinarian preparing for pancreatic surgery

Comparison of Treatment Options

Item	Surgery	Medical therapy	Dietary management alone
Hypoglycemia control effect	Very high	Moderate	Low
Average survival time	About 12–18 months	Several months–1 year	Several months
Applicability with metastasis	Limited	Possible	Adjunctive
Cost burden	High	Moderate (ongoing)	Low
Caregiver management difficulty	Low (post-surgery)	Moderate	High

Survival time varies greatly depending on the individual's condition and disease stage; decide after consulting your veterinarian.

Home Care Management

Insulinoma is a chronic condition, and consistent care at home can significantly improve your pet’s quality of life. - Feed small, frequent meals: Divide daily food into 4–6 meals to minimize blood sugar fluctuations. - High-protein, complex-carbohydrate diet: Simple sugars can trigger rapid reactive hypoglycemia. - Keep emergency sugar sources on hand: Always have honey or sugar syrup nearby. - Moderate exercise intensity: Vigorous walks can induce hypoglycemia; opt for short, gentle outings instead. - Record symptoms: Note the timing, duration, and triggers of any seizures to share with your veterinarian during visits.

Senior dogs should eat small, frequent meals.

Points for Preventing Recurrence and Metastasis

Even if a tumor is surgically removed, metastasis to the liver or lymph nodes may already be present. In fact, studies show that in nearly all cases, hypoglycemia can recur over time due to metastasis. Therefore, it is important to regularly monitor blood glucose levels and perform abdominal ultrasounds after surgery. If signs of hypoglycemia—such as collapse, seizures, or hindlimb weakness—recur, please have your pet undergo a fasting blood glucose test immediately, regardless of breed or age, to check for recurrence or metastasis.

Reviewed by a veterinarian

Dr. Tony — Punnawat Phongkittirak

Veterinarian

A veterinarian who majored in veterinary medicine at Khon Kaen University, Thailand, and completed the IVSA program at North Carolina State University in the United States. Drawing on clinical experience at animal hospitals, he works in the pet healthcare field and is dedicated to building a digital care environment that connects pet parents with veterinarians.

Frequently Asked Questions

Can an insulinoma be cured with surgery?

The goal is long-term management rather than a complete cure. Because the malignancy rate is high, microscopic metastasis may still be present, but many dogs can live symptom-free for over one to two years after surgery.

Is medication alone sufficient?

If surgery isn’t an option, we can manage hypoglycemia with diazoxide and steroids (prednisolone). However, since the tumor itself continues to grow, symptoms may gradually worsen.

Should I check blood sugar levels at home?

If your veterinarian recommends it, regularly monitor your pet’s fasting and post-meal blood sugar levels using a home glucose meter or a continuous glucose monitoring system. Keeping a record of these readings and sharing them during veterinary visits can be very helpful in adjusting medication dosages.

What first aid can I do at home if my pet has a hypoglycemic seizure?

Apply honey or sugar syrup to the gums and the inside of the tongue. If the animal is conscious, you may offer a small amount of food. Afterward, it is essential to take the animal to a veterinary clinic.

Which breeds should be especially cautious?

Based on current veterinary textbooks, it’s difficult to definitively say that certain breeds are at higher risk. However, since insulinomas are the most common functional neuroendocrine tumors in dogs, any dog showing recurring signs of hypoglycemia—such as collapsing, seizures, or hind limb weakness—should have a fasting blood glucose test, regardless of breed.

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References

[1] Clinical Medicine of the Dog and Cat, 4th Ed — Chapter 12 Endocrine Disorders

[2] Plumb's Veterinary Drug Handbook, 10th Ed — Insulin, Diazoxide

[3] Handbook of Veterinary Pharmacology — Hormones and Agents Affecting Endocrine Function

[4] Withrow & MacEwen's Small Animal Clinical Oncology — Endocrine Tumors