Functional Islet Cell Tumors (Insulinomas)
If tumors are present in the islet cells it is most likely that they produce and/or secrete the hormones that are normally secreted by the gland. Beta cells that secrete insulin are affected by the most common pancreatic islet tumor, called an insulinoma. These tumors are most common in dogs that are middle aged and older.
Visible signs of these tumors usually result from excessive insulin secretion. This excess secretion causes low blood sugar, or hypoglycemia, which typically presents with fatigue after exercise, lack of coordination, muscle twitching, general weakness, confusion, and sometimes a change in disposition or temperament. Dogs may become easily agitated, become very restless or excited, experience periodic seizures in some cases, and can may even collapse or appear to have fainted.
At first signs will be infrequent, but as the tumor grows and the disease progresses they will become more obvious and happen more often. It is common for attacks to be brought on my exercise, eating, which lowers blood sugar levels due to the release of insulin, or fasting. After glucose treatment is administered, though, symptoms generally resolve fairly quickly.
It is important to have dogs treated quickly when symptoms are present as prolonged and/or severe episodes of low blood sugar that recur frequently can sometimes result in irreversible brain damage. Generally veterinarians will diagnose the condition based on a dog’s history of collapse, seizures, and weakness along with laboratory tests indicating low blood sugar.
Surgical removal of the tumor can often correct the nervous system symptoms and low blood sugar, except in cases where permanent damage has already occurred. However, it is possible for blood sugar levels to remain low if the tumor has already spread pre-surgery. In most cases insulinomas are malignant, and dogs with malignant tumors usually only have a year or so to live. In some cases quality of life can be maintained through diet modification and treatment with glucocorticoids.
Gastrin-secreting Islet Cell Tumors (Gastrinomas)
Gastrin is a hormone that stimulates the release of gastric acids in the stomach. Normally this secretion only occurs in the small intestine. However, it can also be secreted by way of pancreatic islet cell tumors called gastrinomas in rare cases.
Loss of appetite, intermittent diarrhea, usually with dark blood, dehydration, weight loss, and vomiting up blood are common signs of gastrinoma. Most of these symptoms are caused by stomach ulcers which develop because of too much gastrin in the stomach. Exploratory surgery can be done in dogs with repeated intestinal or stomach ulcers to check for pancreatic tumors. However, by this point pancreatic cancer has been, in all known cases, untreatable due to its having spread to other areas. Dogs are usually prescribed medication to treat the stomach and intestinal ulcers so that they can be more comfortable.