Diabetes in dogs 

Diabetes is the most common hormonal metabolic disease affecting dogs and is typically accompanied by increased fluid consumption and regular urination. Females and breeds like the Samoyed or Miniature Schnauzer show an increased risk of falling ill with diabetes. The disease is divided into diabetes mellitus and diabetes insipidus, since their development process is different.

Causes of diabetes mellitus

Diabetes mellitus is by far the most common form. It is a complex syndrome that results from an increased blood sugar level due to a lack of insulin. The pancreas is divided into an endocrine and exocrine section. The endocrine part is made up of beta cells, which form the anabolic hormone insulin. When insulin is released into the blood, it causes sugar to be absorbed into the cells and more glycogen to be produced. If the concentration increases to a certain value, the formation of sugar is inhibited (gluconeogenesis) as well glycogen being broken down into sugar (glycolysis). At the same time, the anabolic hormone leads to the formation of protein and fats.

There are numerous causes of diabetes mellitus. This form of the disease can be split into four forms:

• Type 1 (juvenile diabetes mellitus) = absolute insulin deficiency: the body forms protective proteins (antibodies) against the pancreas’ own cells. Accordingly, less insulin is produced or none at all. Sugar is no longer absorbed into the cells and remains in the blood vessels. This type is most commonly observed amongst dogs.
• Type 2 (adult diabetes mellitus) = relative insulin deficiency: the cause is a loss of function of the beta cells or insulin resistance. The latter means that although sufficient insulin is formed, it no longer has any effect on the metabolism. This type is predominantly found amongst cats.
• Secondary diabetes mellitus: this form is caused by several underlying diseases such as adrenal gland hyper-function (Cushing syndrome) or the administration of glucocorticoids (cortisone), which can lead to insulin resistance. Further causes are pancreatitis, obesity and infections.
• Gestational diabetes: pregnancy hormones like progesterone play a significant role here, since they lead to an increase in the blood sugar level.

Causes of diabetes insipidus (large quantities of urine)

In contrast to diabetes mellitus, diabetes insipidus is more rarely found. The causes are split into central and renal diabetes insipidus. Both forms can be congenital or secondary due to other diseases and traumas, with the antidiuretic hormone (ADH) at the centre of the process. It is formed in the hypothalamus (part of the diencephalon) and normally has the function of regaining water from the primary urine. However, ADH deficiency is a feature of central diabetes insipidus, whilst renal diabetes insipidus is caused by the inability of ADH to bind to its accompanying receptors. Increased urination is typical here.

Symptoms

Diabetes in dogs can show the following symptoms:

• Principal symptom: increased fluid consumption and urination (polyuria, polydipsia)
• Weight loss despite increased appetite (polyphagia)
• Listlessness and fatigue
• Cataracts with sudden blindness
• Poor fur quality
• Poor wound healing
• Diabetic ketoacidosis (DKA): if diabetes is treated incorrectly or not discovered, the result can be that the body cells no longer receive sufficient sugar as a source of energy. The consequence is excessive production of ketone bodies by splitting fats. The increased concentration of ketosis ultimately leads to hyperacidity of the blood (acidosis). The resulting electrolyte imbalances can end in vomiting, weakness and life-threatening conditions.

Diagnosis

Every trip to the vet begins with a thorough interview of the owner (anamnesis). This is very important for diagnostic purposes, because important clues such as increased water consumption and listlessness can point to diabetes in dogs. After the anamnesis, a clinical general examination takes place in which the dog’s general condition is assessed. Afterwards, the vet carries out a special examination. Blood and urine samples are taken from the dog in order to determine vital parameters like the glucose level. Since the blood sugar level is subject to strong fluctuations due to food or stress, for instance, it’s recommended to measure the fructosamine.

These are certain proteins that can be evaluated as a long-term parameter (over 1-3 weeks) of the blood sugar level. If pancreatitis is suspected, specific auxiliary values such as amylase and lipase can also be determined. The suspicion of diabetes is strengthened with increased sugar and protein content and possibly ketones as well as an altered urine specific gravity. Since the high blood sugar level can lead to deposits of sugar in the eyes, the risk of suffering from cataracts is very high. Hence, blood pressure should always be taken and the eyes tested.

An ADH test can be carried out in order to differentiate diabetes insipidus from diabetes mellitus. This involves the dog being administered ADH and the improvement of water retention then being measured. If there is an improvement, this is central diabetes insipidus. Another method is known as the thirst test, for which the dog has to remain thirsty for several hours after emptying its bladder. Afterwards, the amount of urine that has formed is measured. If it it hasn’t decreased, this is diabetes insipidus.

Treatment

Depending on the cause, a successful treatment is comprised differently:

Diabetes mellitus:

• Administration of insulin twice per day (short-, intermediate- and long-acting insulin)
• Dietary measures: calculate calorie requirements, low amount of poorly digestible carbohydrates and fats, high proportion of raw fibres
• Regular exercise
• Regular monitoring of the blood sugar level and other parameters
• DKA: immediate administration of infusions, electrolytes and insulin, as well as ongoing monitoring by a vet
• Oral anti-diabetics show no effect in dogs

Diabetes insipidus:

• Central form: administration of synthetic ADH
• Renal form: treatment of the underlying diseases, reduced salt consumption

Gestational diabetes:

• Timely castration/neutering
• Potentially lifelong insulin treatment

Prognosis

The prognosis of diabetes mellitus depends on complications and the success of treatment. The prognosis is good if the sick dog adjusts well to insulin. If it already shows complications and struggles to adjust to insulin, this could result in limited quality of life. The prognosis of central diabetes insipidus is generally favourable, whilst that of renal diabetes insipidus depends on the underlying disease.

Prevention

It is almost impossible to avoid diabetes in dogs. However, neutering females at an early stage, a balanced and healthy diet and regular exercise can reduce the risk.

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