By Chris Holm
Endocrine disorders are some of the top life threatening diseases that affect older dogs, but can also affect younger dogs as well. One of the most common endocrine diseases seen in dogs is Diabetes Mellitus. Diabetes is a disease where the animal’s body cannot utilize glucose properly. Insulin becomes deficient and leads to the accumulation of glucose within the body, because it can no longer be up taken into the cells.
Glucose is a type of simple sugar that the body uses as the main source of energy for the sustainability of cells. In order for the body to utilize glucose as a source of energy, there are several steps that must occur. Sugars come from various food sources. Once in the intestine and digested, sugars are up taken by cells that line the intestines . After sugars are absorbed into the cells, they are converted into simple sugars such as glucose. Simple sugars such as glucose can then be absorbed into the bloodstream and distributed throughout the body’s tissues and cells. However, the most limiting step of the process includes the presence of insulin being required for the uptake of glucose from the bloodstream into the cells. Without insulin properly facilitating the uptake of glucose, it cannot be absorbed into the cells and will continuously accumulate within the bloodstream until it is excreted in excess into the urine .
The accumulation of excess glucose within the bloodstream with decreased insulin production in dogs is diagnosed as Diabetes Mellitus. The complete pathogenesis of the disease is not known specifically. There are many factors that can play a role in the disease process. Some of the most common breeds that are predisposed to developing diabetes at younger ages or at some time period in their lifespan include Terriers, miniature Poodles, and Schnauzers [1, 4]. For dogs, the most common signalment seen are females which are twice as common as males and middle aged dogs between four and fourteen years of age . One of the main predisposing factors that leads to the development of diabetes is obesity. Several other factors that may also lead to the development of the disease include chronic pancreatitis, glucocorticoid administration, and infections .
There are many reasons why excess glucose accumulates within the bloodstream. Insulin deficiency is a major contributing factor that can lead to the accumulation of glucose within the body. Insulin production can be interfered with by diseases that affect the pancreas. The beta cells of the endocrine pancreas produce insulin normally within the body to regulate the uptake of glucose . The most common cause of diabetes in dogs is absolute insulin deficiency which mimics Type 1 diabetes in humans [1, 3]. Diabetes Mellitus is characterized by the destruction of pancreatic beta cells that leads to absolute insulin deficiency . Absolute insulin deficiency makes the therapy of the disease insulin dependent, which means that insulin must be administered and supplied to the body for the regulation of blood glucose . The exact pathogenesis that leads to the beta cell destruction is unknown, however there are many immune-mediated processes that are suspected . There is evidence in recent findings that have found circulating autoantibodies against beta cells in 50% of dogs with diabetes mellitus . The autoantibodies target an antigen in the beta cells that leads to the destruction of the cells and leads to the dog being completely insulin dependent .
Presenting complaints for diabetes mellitus can vary depending on the case and the dog itself. The most classical clinical signs of a dog with diabetes mellitus include polyuria, polydipsia, weight loss, an increased appetite, and lethargy . Polyuria is a scientific term used to describe increased urination, while polydipsia is a term used to describe increased water intake. The initial diagnosis is usually straight forward and can be easily diagnosed. A definitive diagnosis is based on the clinical signs, hyperglycemia, and glucosuria . Diagnostics may include a complete blood count, serum biochemistry, urinalysis, urine culture, abdominal radiographs, and abdominal ultrasound . With diabetes mellitus, a blood glucose is usually over 350 milligrams per deciliter with glucosuria and increased fructosamines . In some situations, stress can lead to the development of increased glucose, however it can be differentiated by having a blood glucose less than 250 milligrams per deciliter and no glucose in the urine [1, 4].
The treatment of diabetes mellitus can include multiple modalities. Like said earlier, one of the top predisposing factors includes obesity. Once diagnosed with diabetes mellitus in an obese dog, a diet plan needs to be implemented immediately. A proper diet including increased fiber, decreased simple sugars, and decreased fat along with exercise and oral hypoglycemics can be a start to the management of diabetes . There is no treatment that will cure diabetes mellitus. The goal of therapy is to resolve clinical signs, avoid insulin-induced hypoglycemia, and to resume the usual lifestyle and exercise levels of the patient . The mainstay of therapy in dogs is the administration of exogenous insulin. Exogenous insulin is made outside of the body, and usually comes from other animal species such as bovine insulin which comes from cows . Choosing the correct insulin for the patient can vary based on the patient at hand and the severity of the disease. There are several types of insulin that can range from rapid action and short duration to sustained action and long duration. The specific type depends on the situation at hand and the amount of destruction that the dog has to the pancreatic beta cells . Choosing the correct insulin and dosage can lead to the proper treatment and lifelong management for the patient.
Canine diabetes mellitus is a common disease seen in middle to older aged dogs. This is a disease that can lead to the death of dogs, however if caught early it can successively be managed throughout the life of the patient. Treatment can be managed with a healthy diet and the administration of insulin. The prognosis of the disease is good to excellent with the proper and consistent management.
- Lathan, Patty. Diabetes Mellitus in Dogs and Cats. February 8, 2015. Mississippi State University College of Veterinary Medicine Small Animal Medicine Course.
- Diabetes in Pets. . Copyright © 2016 American Veterinary Medical Association.
- Kim et al. Anti-Insulin Immune Responses are Detectable in Dogs with Spontaneous Diabetes. PLOS ONE | DOI:10.1371/journal.pone.0152397. March 31, 2016.
- Fleeman, L. and Rand, J. Management of Canine Diabetes. Veterinary Clinics of North America: Small Animal Practice. Volume 31. Number 5. September 2001.