Diabetes

Diabetes is a very common disease in humans & it is becoming increasingly diagnosed in older pets too. It is a serious condition that if left unchecked can lead to complications that can kill your pet. An early diagnosis is essential as we can start to get the condition under control before the disease can cause problems for your pet.

Diabetes Mellitus is a group of conditions in which there is a deficiency of the hormone insulin or an insensitivity to it. Insulin is produced in the islet cells of the pancreas and is normally responsible for controlling blood concentrations of the body’s main fuel, glucose. In normal animals, insulin does this by preventing glucose production by the liver and ensuring that excess glucose derived from food which is not needed for energy is put into body stores.

In a diabetic animal there is insufficient insulin to switch off glucose production by the liver or to efficiently store excess glucose derived from energy giving foods. This means that the blood concentration of glucose rises and eventually exceeds a level beyond which the kidneys let glucose leak into the urine. This loss of glucose in urine takes water with it by a process called osmosis and causes larger volumes of urine to be produced than normal. The excessive loss of water in urine is compensated for by thirstiness and increased water consumption. The principal clinical signs of an animal with diabetes mellitus are therefore polyuria (excessive urination) and polydipsia (excessive water consumption). In addition, diabetic animals tend to lose weight because they breakdown stores of fat and protein (muscle) to make glucose and ketones (an alternative fuel) in the liver. Other clinical signs diabetics may include: cataracts, polyphagia (increased appetite), exercise intolerance and recurrent infections. If the production of ketones by the liver is excessive a condition called ketoacidosis occurs which is eventually fatal if it is left untreated.

Therapy

Oral hypoglycemics

Oral hypoglycemics are tablets used in the treatment of human diabetes mellitus which can lower blood glucose in some cases. In general, they are not useful for the treatment of diabetes mellitus in dogs but are some use in a small proportion of diabetic cats.

Insulin

Insulin is the treatment of choice for diabetes mellitus in animals. Insulin must be given by injection because it is a protein and would be digested in the intestine if it was given as a tablet. Insulin is available as pharmacological preparations for subcutaneous injection which have been formulated to slow its absorption and prolong its action. It therefore needs to be given once or twice daily by injection.

Insulin products have to be treated carefully. They must be thoroughly kept refrigerated mixed prior to use and must not be frozen, heated or shaken vigorously.

Stabilization

Unfortunately, there is no standard dose for insulin which can be applied to all animals. Each diabetic animal has to have its dose tailored to its individual needs which is done over a stabilization period. After such a period, maintenance insulin doses should remain relatively constant. In order to achieve stable control of a diabetic animal’s blood glucose by insulin, all the other factors which affect blood glucose concentration must be kept constant from day to day. These factors include the composition, volume and timing of meals and the amount of exercise the animal gets.

To keep diet constant from day to day it is best to use commercially produced rather than home made diets. Certain prescription or veterinary diets can be a useful adjunct to insulin therapy such as Royal Canin Diabetic, Hill’s w/d or r/d. If special diets are unavailable then standard canned pet foods are acceptable.

There are a number of different ways to stabilize a diabetic animal. Some dogs are managed well with once daily injections but most will require twice daily. The eventual dose of insulin will be determined using blood glucose measurements taken by the veterinarian. At the start of treatment a short period of hospitalisation is usually necessary but after this the animal will only have to come into the surgery for the day.

After stabilization has started the veterinarian will have to create a serial blood glucose curve by repeated measurements of blood glucose regularly throughout the day. Such a curve is  used to decide if the dog needs twice daily injections of insulin and over time together with other blood parameter to decide the dose of insulin necessary.

The insulin treatment of cats is similar to that of dogs but requires twice daily injections of insulin because cats metabolize insulin more rapidly than dogs.

One disadvantage to relying solely on pre-injection urine or blood glucose results is a phenomenon known as Somogyi overswing or insulin induced hyperglycemia (high blood sugar). This is when an excessive insulin dose lowers blood glucose too far and the body responds to this potentially life threatening situation by producing hormones which are antagonistic to the effects of insulin. The release of these hormones causes blood glucose to rise again, often to very high levels which can spill over into the urine and produce strong positive morning urine glucose results. If adequate care is not taken, these results can be mis-interpreted by an insulin adjustment protocol as indicating a requirement for an increase in dose. Such an increase will, in fact, only make matters worse. The possibility of inducing Somogyi overswing can be reduced by measuring and interpreting the blood glucose curve and other blood tests before making insulin dose adjustments.