Before discussing diabetes mellitus in dogs, let us review pancreatic function at first. The pancreas consists of many different cell types, each of which has a specific and unique function that contributes to the production of hormones and digestive enzymes. Enzymes that are crucial to digesting complex dietary substances such as complex carbohydrates, triglycerides, and proteins are produced by the exocrine pancreas. This organ also secretes copious amounts of a hormone called bicarbonate, which helps protect against stomach acid.
The exocrine pancreas, however, is mostly associated with digestion. The endocrine pancreas is the “main” pancreas, and is responsible for producing glucagon and insulin, hormones that help to regulate blood sugar levels in the body. All disorders discussed below deal with the endocrine pancreas.
The pancreas consists of the islets of Langerhans, which consist of three varieties of cells, called beta cells, responsible for the production of a unique hormone. Most of these beta cells are responsible for producing insulin. Every single organ in the body, whether directly or indirectly, is affected by insulin, most specifically the liver, fat cells, and muscle. Essentially, insulin speeds up the transfer of sugar, or glucose, and other bodily compounds into cells throughout the body. Additionally, fat, protein, and carbohydrate breakdown are decreased by insulin.
The islets of Langerhans also consist of two other types of cells which are instrumental in the production of glucagon and somatostatin, two different hormones. Glucagon is released whenever blood sugar levels in the body drop. It helps break down stored carbohydrates for use as glucose, giving the body energy.
Insulin and glucagon are teammates of sorts that work together to ensure that glucose levels and the levels of other crucial bodily fluids are kept in relatively narrow concentrations. Glucagon is instrumental in controlling the release of glucose from the liver, and insulin oversees the transport of glucose to various tissues throughout the body.
Diabetes mellitus, which is usually just referred to as diabetes, is a chronic condition wherein carbohydrate metabolism become disordered due to either a deficiency of or resistance to insulin. This condition is more common in middle-aged dogs, and females are disproportionately affected. Nearly twice as many female dogs come down with the disease as opposed to males. Certain breeds are more affected, as well, especially small breeds like Schnauzers, Beagles, Cairn Terriers, Miniature Poodles, and Dachshunds. However, any breed can be affected by diabetes.
Many bodily mechanisms are involved in decreasing insulin secretion and production, but regardless of the mechanism the result is usually the destruction of islet cells. Many dogs with Cushing’s disease also have insulin resistance or diabetes. Treating dogs long term with glucocorticoids or progestins can often result in the development of diabetes mellitus. When un-spayed female dogs go into their heat cycles they produce progesterone, a hormone that can lead to high blood sugar and insulin resistance. If dogs are obese they run the risk of being insulin resistant. It also appears that higher levels of glucagon may also contribute to the development of high blood sugar via the release of glucose from liver stores.
Diabetes often develops gradually, and it can be difficult to notice signs in the early stages. Increased thirst and urination as well as increased appetite and sudden weight loss are common signs of diabetes in animals. Chronic or recurring infections are also common in diabetic animals, as well as an enlarged liver. If diabetes mellitus is poorly controlled dogs can develop cataracts. The most common diagnostic indicator of diabetes is finding high blood sugar levels in the blood after fasting for a period of time.
Owners who have an understanding of diabetes and maintain daily care for their pets are more likely to see a positive outcome. Weight loss, insulin injections, dietary changes, and, in some cases, medication taken orally are common treatments for dogs with diabetes. Animals may be hospitalized for a day or two after diagnosis for monitoring, blood sample collection, and blood sugar level readings. Using this information veterinarians create a plan for timing of meals, dosage of insulin and timing between doses, and other standard care planning. Once the initial stabilization is complete the veterinarian will provide instructions and possibly give paperwork to the pet owner on how to manage their new regimen at home. The pet will need to be periodically reevaluated to ensure that the dog’s diabetes is being controlled properly and, if appropriate, treatment changes are made in a timely fashion.