Insulinoma in Dogs

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Overview of Canine Insulinoma

An insulinoma is a malignant tumor of the pancreas that secretes excessive amounts of insulin leading to hypoglycemia (low blood sugar concentration). Insulinomas usually occur in middle-aged to older dogs, usually eight to twelve years of age. They are very rare in cats and there is no apparent gender predilection.

Insulinomas can occur in any breed of dog with mixed breed dogs most commonly affected. Among purebred dogs, Irish setters, German shepherds, boxers, golden retrievers, poodles, and Labrador retrievers have a higher incidence. Medium to large-sized breeds of dogs are most commonly affected.

The excessive secretion of insulin by these tumors causes hypoglycemia and clinical symptoms of hypoglycemia.

What to Watch For

  • Seizures
  • Collapse
  • Fainting (also called syncope)
  • Generalized weakness
  • Hind limb weakness
  • Lethargy
  • Incoordination
  • Muscle tremors
  • Unusual behavior
  • Polyphagia or increased appetite
  • Exercise intolerance
  • Shaking
  • Trembling
  • Nervousness
  • Dilated pupils
  • Blindness
  • Diagnosis of Insulinoma in Dogs

    Diagnostic tests are needed to identify insulinoma and exclude other diseases. Your veterinarian may recommend the following:

  • A complete blood count (CBC or hemogram) to identify infection, inflammation, anemia, or low platelet count
  • Serum biochemistry tests to identify hypoglycemia, evaluate your pet’s general health and determine the effect of the insulinoma on other body systems
  • Urinalysis to evaluate kidney function and identify urinary infection
  • Serum insulin concentration paired with blood glucose concentration. The hallmark of insulinoma is the presence of a normal or high serum insulin concentration at the same time that the patient has a low blood glucose concentration. In patients with hypoglycemia from other causes, serum insulin concentrations usually are very low at the same time the patient is hypoglycemic.
  • Chest X-rays to determine if the insulinoma has spread to the lungs – a very rare occurrence
  • Abdominal X-rays to evaluate liver, spleen, and kidneys. Insulinomas are very small and cannot be identified on plain X-rays of the abdomen.
  • Abdominal ultrasound to evaluate the pancreas for presence of an insulinoma and the liver and abdominal lymph nodes for local spread of the insulinoma. Regional lymph nodes and liver are the most common sites for spread of insulinoma.

    Treatment of Insulinoma in Dogs

    Treatment for acute insulinoma may include the following:

  • Surgery to remove the tumor
  • Medical therapy
  • Emergency treatment with intravenous glucose to increase the patient’s blood glucose concentration

    Long-term treatment:

  • Dietary therapy
  • Cortisone-like drugs like prednisone
  • Diazoxide, which is a drug that inhibits release of insulin from the insulinoma
  • Somatostatin
  • Chemotherapy, although it is not very effective for insulinoma
  • Home Care and Prevention for Insulinoma

    Administer as directed any medications prescribed by your veterinarian and follow any special dietary recommendations. Watch your dog carefully for signs of hypoglycemia and administer corn syrup orally if you see signs of hypoglycemia, such as seizures, weakness or muscle tremors.

    Observe your dog’s general activity level, appetite and attitude. Watch for recurrence of clinical symptoms of hypoglycemia that may indicate recurrence of the tumor. Feed frequent small meals of a high carbohydrate diet to maintain adequate blood sugar concentration.

    Schedule regular follow-up visits with your veterinarian to monitor your dog’s progress and promptly identify any recurrence of hypoglycemia and insulinoma.

    Keep your dog’s exercise and activity level relatively constant. Avoid intensive exercise or provide high carbohydrate snacks before exercise.

    The cause of insulinomas is unknown, and consequently there is no way to prevent development. You can prevent a hypoglycemic crisis by following the dietary, exercise, and medical recommendations of your veterinarian.

    Information In-depth for Insulinoma in Dogs

    The pancreas contains collections of cells called islets of Langerhans. Normal islets contain four cell types: alpha, beta, delta, and F cells. Each of these cell types produces a specific hormone. Beta cells produce insulin. Excessive amounts of insulin are released into the bloodstream when a malignant tumor (insulinoma) develops from the beta cells. In normal animals, insulin works with other hormones to maintain blood sugar concentration in the normal range (approximately 70 to 100 milligrams per deciliters of blood). Excessive secretion of insulin by the beta cell tumor (insulinoma) causes the blood sugar concentration to fall below the normal range (hypoglycemia) with several different possible symptoms including:

  • Seizures. Seizures are the most common symptom in dogs with insulinomas and occur in 68 percent of affected dogs.
  • Generalized weakness
  • Collapse or fainting (also called syncope)
  • Hind limb weakness
  • Lethargy
  • Incoordination
  • Muscle tremors
  • Excessive food consumption, also called polyphagia. Presumably dogs eat more in an attempt to maintain their blood sugar concentration in the normal range.
  • Exercise intolerance
  • Weight gain due to the growth-promoting (or anabolic) effects of insulin

    Most dogs with insulinomas display some of the symptoms listed above, but these symptoms tend to be intermittent and physical examination at the veterinarian’s office usually is unremarkable. Other medical problems can lead to symptoms similar to those encountered in insulinoma. It is important to exclude these conditions before establishing a definitive diagnosis:

  • Some non-pancreatic tumors also can cause low blood sugar concentration, especially liver tumors, called hepatomas. There are several potential explanations why other tumors may cause low blood sugar concentration, including excessive glucose utilization by a very large tumor or secretion of a substance that mimics insulin in its effects.
  • Severe liver disease. The liver is a major storage site for glucose. Hypoglycemia may develop in advanced or severe liver disease when more than 70 percent of the liver is compromised.
  • Sepsis. Severe body-wide bacterial infection with widespread dissemination through the bloodstream may cause hypoglycemia, possibly due to increased utilization of the glucose by the bacteria.
  • Insulin overdose. Hypoglycemia may occur as a result of an accidental overdose of insulin in a diabetic animal.
  • Hypoadrenocorticism. Inadequate cortisol production by the adrenal glands, also called Addison’s disease, may result from inadequate production and mobilization of glucose.
  • Hunting dog hypoglycemia. This poorly understood condition of nervous, thin hunting dogs may result in depletion of glucose stores in the liver and development of hypoglycemia.
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