Insulinoma in Dogs
Insulinomas are malignant neoplasms -- fast growing cancer cells -- of the beta cells in the pancreas. The beta cells primarily secrete insulin, among other hormones. Insulin produces a variety of effects in the body -- the primary one being to regulate glucose levels throughout the body's cells. Because insulinomas secrete excessive insulin, the blood stream becomes low in glucose (a condition referred to as hypoglycemia), which causes weakness or neurological problems.
Symptoms and Types
The most common symptom of an insulinoma is physical collapse, or loss of consciousness (syncope). Seizures, extreme weakness, and other neurological abnormalities are also common. Because the insulin is released periodically, symptoms are not consistent and frequency is not necessarily predictable.
If your dog should collapse and a blood sample indicates low glucose, insulinoma will be highly suspected and your veterinarian will need to follow through with further tests to confirm it. However, multiple blood samples may need to be taken over a period of time to determine if there is a persistent low glucose concentration. Your doctor will need to determine the insulin concentration at the lowest glucose concentration. Withold food from your dog before tests are performed is essential for determining true glucose levels - your veterinarian will advise you on the appropriate way to conduct these short term fasts for your dog.
An amended insulin:glucose ratio (AIGR) may be useful when your dog's insulin level is low, yet still in the normal range. Insulinoma is still suspected in these type of cases. If the insulin level is inappropriately high for the decreased glucose level, insulinoma may still be present.
Ultrasound, computed tomography (CT), or magnetic resonance imaging (MRI) can be helpful in determining the extent of the pancreatic tumor and how much it is metastasizing. Typically insulinomas do not metastasize to the lungs; however, chest x-rays may indicate other neoplasias as a cause of persistently decreased glucose. Scintigraphy, a form of imaging using radioactive isotopes to identify abnormal tissue, can also be used to identify the location of primary insulinomas and metastasis.