Diabetes mellitus is a common endocrinopathy in middle-aged and older dogs and is a complex disorder of carbohydrate, protein, and lipid metabolism. This disorder, which is the result of a relative or absolute insulin deficiency or of peripheral cell insensitivity to insulin, is characterized by high blood glucose concentrations such that the renal threshold is exceeded. As a result, glucose is excreted in the urine.
The osmotic action of glucose leads to polyuria and, through loss of fluid, to polydipsia. In addition, metabolism is impaired so that the general condition of the animal deteriorates, ultimately leading to death.
Insulin is synthesized and released from beta cells in the pancreatic islets. Insulin assists with cellular uptake of glucose from the bloodstream, thus exerting a hypoglycemic effect. Within cells, insulin promotes anabolism (such as synthesis of glycogen, fatty acids, and proteins) and counters catabolic events (reduces gluconeogenesis and inhibits fat and glycogen breakdown).
Whereas insulin lowers blood glucose, there are opposing hormones (glucagon, cortisol, progesterone, adrenaline, thyroid hormone, and growth hormone) that act to increase blood glucose. It is important to consider these counter-regulatory hormones, because changes in their blood concentrations will interfere with insulin actions. Changes in these hormones can occur in natural physiological conditions, in disease states, or as a consequence of drug administration.
In the absence of sufficient insulin, diabetic dogs will switch from glucose to fat metabolism for cellular energy. While this is initially beneficial, fat metabolism in unrecognized or untreated diabetics typically progresses to ketoacidosis and ultimately to death.
Diabetes mellitus is not related to diabetes insipidus, an uncommon condition that occurs when the kidneys are unable to regulate fluids in the body. Diabetes insipidus is characterized by a deficiency or inadequate response to a hormone called vasopressin.
Disease prevalence and risk factors
Estimates of the prevalence of diabetes mellitus in dogs is up to 1 in 100.10 The diagnosis is often preceded or accompanied by obesity.
Certain breeds appear to be at greater risk for developing canine diabetes:8
- Cocker Spaniel
- Doberman Pinscher
- German Shepherd
- Golden Retriever
- Labrador Retriever
- Toy Poodle
Diabetes typically occurs when dogs are between 4 to 14 years old. Unspayed female dogs are twice as likely as male dogs to suffer from diabetes.
Most forms of diabetes can be successfully managed with insulin, the cornerstone of successful management, but dietary adjustments and a regular lifestyle are also important.
The prognosis for diabetes mellitus depends mainly on:
- The cause
- An early diagnosis
- Adequate therapy
In general, the prognosis is very good, provided that diagnosis is made at an early stage and therapy is administered properly. Open communication between client and veterinarian is also extremely important. Your encouragement of the client will largely influence the dog owner’s motivation and compliance with therapy. Clients need to fully understand the disease to help achieve and maintain good diabetic stability and be highly motivated and committed to the management of their dog.
The clinical staff also has an important role in providing detailed client education, instruction, and encouragement. So they should understand the basics of diabetes mellitus and its management.