Diabetes Insipidus

At least a quarter of all dogs euthanized or turned into shelters are given up because of behavior-related issues. Near the top of the list of reasons for euthanasia and being turned into shelters is house soiling. Therefore, whenever an inappropriate elimination behavior develops, look first for an underlying medical condition before starting training or behavior modification exercises. One of the several diseases that impair a dog's elimination is diabetes insipidus (DI), a disease that is characterized by frequent urination, excretion of large amounts of dilute urine, and excessive thirst. Despite its name, diabetes insipidus is not related to the more commonly known diabetes mellitus, or involves insulin or sugar metabolism. However, these two diseases can have similar signs and symptoms, such as excessive thirst and excessive urination.

Your dog's body has a complex system for balancing the volume and composition of body fluids. The kidneys remove extra body fluids from the bloodstream, which are stored in the bladder as urine. If the fluid regulation system is working properly, the kidneys make less urine to conserve fluid when the body is losing water. The kidneys also make less urine at night when the body's metabolic processes are slower. The hypothalamus makes antidiuretic hormone (ADH) vasopressin, which directs the kidneys to make less urine. In order to keep the volume and composition of body fluids balanced, the rate of fluid intake is governed by thirst, while the rate of excretion is governed by the production of ADH. Diabetes insipidus occurs when this precise system for regulating the kidneys' handling of fluids is disrupted.



There are two broad types of diabetes insipidus: cranial (central) diabetes insipidus (CDI) and nephrogenic diabetes insipidus. With central diabetes insipidus, the pituitary gland does not secrete enough ADH, whereas in nephrogenic diabetes insipidus it's the kidneys that do not respond normally to the hormone. Damage to the pituitary gland can be caused by a disease, head injury, neurosurgery, or genetic disorder. Dogs with acquired CDI due to a growing pituitary or hypothalamic tumor may develop neurologic signs including stupor, disorientation, seizures, and tremors.4 The kidneys' ability to respond to ADH can be impaired by drugs or by a chronic disease, including polycystic kidney disease, sickle cell disease, kidney failure, partial blockage of the ureters, and inherited genetic disorders. To treat the ADH deficiency that results from any kind of damage to the hypothalamus or pituitary, a synthetic hormone desmopressin is administered. The treatment may be lifelong.

Dipsogenic diabetes insipidus is the third form of diabetes insipidus that is caused by a defect in or damage to the thirst mechanism, which is located in the hypothalamus. This form of diabetes insipidus results in an abnormal increase in fluid intake and urine output. Because of the excretion of abnormally large volumes of dilute urine, the dog may quickly become dehydrated, if he does not drink enough water, therefore a continuous supply of drinking water must be provided at any time. Even with medication, the urge to urinate can come on very suddenly, and in most cases, the dog will not be able to go more than an hour or so without urinating. A "dog door" leading outside may help to prevent accidents. Desmopressin is not used to treat dipsogenic DI because it may increase fluid retention; this fluid "overload" can lead to water intoxication, a condition that lowers the concentration of sodium in the blood and can seriously damage the brain.

  • Hypothalamus - an area of the brain that produces hormones that control body temperature, hunger, moods, release of hormones from many glands, especially the pituitary gland, sex drive, sleep, and thirst;
  • Pituitary gland - a gland that regulates hormone production and release by other endocrine glands;

References

  1. Susan Thorpe-Vargas and John Cargill. Diabetes Insipidus In Our Best Friends
  2. Nephrogenic Diabetes Insipidus Foundation
  3. The Diabetes Insipidus and Related Disorders Network




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